In the United States, active duty Armed Forces personnel tended to be young, with the majority under the age of 30 years old. In 2023, there were 546,361 U.S. Defense Armed personnel aged 25 and under. In the age group 26 to 30, there were 275,756 Armed Forces personnel.

In 2024, the average age for personnel in the UK Armed Forces overall was 31 years old. The average age of those serving in the British Army was also 31, with the average age rising to 32 for the Royal Navy and Marines, and was 33 for the Royal Air Force (RAF). The average age for officers in the Armed Forces was 37, with this rising to 38 for officers in the Royal Air Force. Personnel falls to historical lows in 2024 Overall, there has been a long-term decline in the size of the armed forces, with the number of personnel declining from over 200,000 in 2000, to around 138,120 by 2024. In fact, the size of the armed forces has been in almost constant decline since the end of World War Two. Britain's retreat from its colonial empire throughout this period removed many of the UK's overseas commitments, with the end of the Cold War also leading to further cuts to personnel. Operational deaths since the Second World War Since 1945 there have been 7,193 operational deaths in the United Kingdom’s armed forces, with the deadliest year occurring in 1951 when there were 851 deaths. This was due to three separate conflicts: the Malayan Emergency, the 1951 Anglo-Egyptian War and the Korean War. Since 1959, there were only three years that had more than 100 operational deaths: 1972, 1973 and 1982. By comparison, between 2016 and 2024, there have been only nine operational deaths, with just one death reported throughout the whole of 2023.

In 2023, 42.14 percent of U.S. men aged 75 years and over were veterans - the highest share of any age group or gender. In comparison, less than one percent of women aged 75 and over were veterans at that time.

In the fiscal year of 2019, 21.39 percent of active-duty enlisted women were of Hispanic origin. The total number of active duty military personnel in 2019 amounted to 1.3 million people.

Ethnicities in the United States The United States is known around the world for the diversity of its population. The Census recognizes six different racial and ethnic categories: White American, Native American and Alaska Native, Asian American, Black or African American, Native Hawaiian and Other Pacific Islander. People of Hispanic or Latino origin are classified as a racially diverse ethnicity.

The largest part of the population, about 61.3 percent, is composed of White Americans. The largest minority in the country are Hispanics with a share of 17.8 percent of the population, followed by Black or African Americans with 13.3 percent. Life in the U.S. and ethnicity However, life in the United States seems to be rather different depending on the race or ethnicity that you belong to. For instance: In 2019, native Hawaiians and other Pacific Islanders had the highest birth rate of 58 per 1,000 women, while the birth rae of white alone, non Hispanic women was 49 children per 1,000 women.

The Black population living in the United States has the highest poverty rate with of all Census races and ethnicities in the United States. About 19.5 percent of the Black population was living with an income lower than the 2020 poverty threshold. The Asian population has the smallest poverty rate in the United States, with about 8.1 percent living in poverty.

The median annual family income in the United States in 2020 earned by Black families was about 57,476 U.S. dollars, while the average family income earned by the Asian population was about 109,448 U.S. dollars. This is more than 25,000 U.S. dollars higher than the U.S. average family income, which was 84,008 U.S. dollars.

In 2025, there were around 137,000 regular personnel serving in the British Armed Forces, compared with 138,000 in the previous year. In the first half of the twentieth century, there were two huge spikes in the number of active personnel which represented the final years of World War One and World War Two, numbering 4.58 million and 4.69 million in 1918 and 1945 respectively. Ever since 1945, the size of the regular armed forces has been in almost constant decline, with the noticeable exception of the early 1950s, when the number of active personnel increased by almost 200,000 because of the Korean War. The winds of change There are several reasons why the number of personnel in Britain’s armed forces has declined. Britain is involved in a far fewer conventional military conflicts today than it was in the past. As the size of Britain’s empire declined rapidly after 1945, so too did the UK's global military commitments. There are also more recent developments, such as the UK government’s Strategic Defence and Security Review of 2010, which outlined personnel would be cut throughout the 2010s to modernize the UK’s armed forces. Recent geopolitical events such as the War in Ukraine have, however, led to commitments from the UK government to spend more on defence, and eventually even a reversal of personnel cuts. Branches of the UK military There are three main branches of the UK armed forces, the British Army, the Royal Navy, the Royal Air Force, and the Royal Marines. Of the 181,000 people serving in the UK’s armed forces in 2025, over half of them were in the British Army, which had around 109,000 personnel. The next largest branch was the Royal Navy at 37,900, followed by the RAF at 34,800 personnel. The average age for people serving in the armed forces was 31 in 2024, with the Royal Air Force having a slightly higher average age group than the other branches, at 33.

During the Second World War, the three Axis powers of Germany, Italy, and Finland mobilized the largest share of their male population. For the Allies, the Soviet Union mobilized the largest share of men, as well as the largest total army of any country, but it was restricted in its ability to mobilize more due to the impact this would have on its economy. Other notable statistics come from the British Empire, where a larger share of men were drafted from Dominions than from the metropole, and there is also a discrepancy between the share of the black and white populations from South Africa.

However, it should be noted that there were many external factors from the war that influenced these figures. For example, gender ratios among the adult populations of many European countries was already skewed due to previous conflicts of the 20th century (namely WWI and the Russian Revolution), whereas the share of the male population eligible to fight in many Asian and African countries was lower than more demographically developed societies, as high child mortality rates meant that the average age of the population was much lower.

In 2024, there were 138,120 personnel serving in the British Armed Forces, compared with 142,0 in the previous year. In the first half of the twentieth century, there were two huge spikes in the number of personnel which represented the final years of World War One and World War Two, with the British Armed Forces numbering 4.58 million and 4.69 million in 1918 and 1945 respectively. Ever since 1945, the size of the UK Armed Forces has been in almost constant decline, with the noticeable exception of the early 1950s, where Britain's armed forces increased by almost 200,000 because of the Korean War. The winds of change There are several reasons why the number of personnel in Britain’s armed forces has declined. Britain is involved in a far fewer conventional military conflicts today than it was in the past. As the size of Britain’s empire declined rapidly after 1945, so too did the UK's global military commitments. There are also more recent developments, such as the UK government’s Strategic Defence and Security Review of 2010, which outlined personnel would be cut throughout the 2010s to modernize the UK’s armed forces. Recent geopolitical events such as Russia's invasion of Ukraine have, however, led to commitments from the UK government to spend more on defence, and possibly even a reversal of personnel cuts. Branches of the UK military There are three main branches of the UK armed forces, the British Army, the Royal Navy, the Royal Air Force, and the Royal Marines. Of the 138,120 people serving in the UK’s armed forces in 2024, over half of them were in the British Army, which had 75,320 personnel. The next largest branch was the RAF at 30,800, followed by the Royal Navy at 32,000 personnel. The average age for people serving in the armed forces was 31 in 2023, with the Royal Air Force having a slightly higher average age group than the other branches, at 33.

Housing conditions of Canadian military families: Canada, provinces and territories, census metropolitan areas and census agglomerations with parts Frequency: Occasional Table: 98-10-0145-01 Release date: 2023-11-15 Geography: Canada, Province or territory, Census metropolitan area, Census agglomeration, Census metropolitan area part, Census agglomeration part Universe: Population aged 17 and over in owner and tenant households with household total income greater than zero in non-reserve, non-farm private households, 2021 Census — 25% Sample data Variable List: Housing indicators (6), Household type of person (10), Tenure including presence of mortgage payments and subsidized housing (7), Structural type of dwelling (10), Age (15D), Gender (3), Military service status (4A) Footnotes: 1 Household type Household type refers to the differentiation of households on the basis of whether they are census family households or non-census-family households. Census family households are those that contain at least one census family. Non-census-family households are either one person living alone or a group of two or more persons who live together but do not constitute a census family. Census family households may be differentiated based on the presence of additional persons (that is, persons not in a census family). 2 Structural type of dwelling 'Structural type' refers to the structural characteristics and/or dwelling configuration, that is, whether the dwelling is a single-detached house, an apartment in a high-rise building, a row house, a mobile home, etc. 3 Age 'Age' refers to the age of a person (or subject) of interest at last birthday (or relative to a specified, well-defined reference date). 4 Gender Gender refers to an individual's personal and social identity as a man, woman or non-binary person (a person who is not exclusively a man or a woman). Gender includes the following concepts: gender identity, which refers to the gender that a person feels internally and individually; gender expression, which refers to the way a person presents their gender, regardless of their gender identity, through body language, aesthetic choices or accessories (e.g., clothes, hairstyle and makeup), which may have traditionally been associated with a specific gender. A person's gender may differ from their sex at birth, and from what is indicated on their current identification or legal documents such as their birth certificate, passport or driver's licence. A person's gender may change over time. Some people may not identify with a specific gender. 5 Given that the non-binary population is small, data aggregation to a two-category gender variable is sometimes necessary to protect the confidentiality of responses provided. In these cases, individuals in the category “non-binary persons” are distributed into the other two gender categories and are denoted by the “+” symbol. 6 Dwelling condition 'Dwelling condition' refers to whether the dwelling is in need of repairs. This does not include desirable remodelling or additions. Housing suitability Housing suitability refers to whether a private household is living in suitable accommodations according to the National Occupancy Standard (NOS); that is, whether the dwelling has enough bedrooms for the size and composition of the household. A household is deemed to be living in suitable accommodations if its dwelling has enough bedrooms, as calculated using the NOS. 'Housing suitability' assesses the required number of bedrooms for a household based on the age, sex, and relationships among household members. An alternative variable, 'persons per room,' considers all rooms in a private dwelling and the number of household members. Housing suitability and the National Occupancy Standard (NOS) on which it is based were developed by Canada Mortgage and Housing Corporation (CMHC) through consultations with provincial housing agencies. Shelter-cost-to-income ratio 'Shelter-cost-to-income ratio' refers to the proportion of average total income of household which is spent on shelter costs. Core housing need Core housing need refers to whether a private household's housing falls below at least one of the indicator thresholds for housing adequacy, affordability or suitability, and would have to spend 30% or more of its total before-tax income to pay the median rent of alternative local housing that is acceptable (attains all three housing indicator thresholds). Housing indicator thresholds are defined as follows: Adequate housing is reported by their residents as not requiring any major repairs. Affordable housing has shelter costs equal to less than 30% of total before-tax household income. Suitable housing has enough bedrooms for the size and composition of resident households according to the National Occupancy Standard (NOS), conceived by the Canada Mortgage and Housing Corporation and provincial and territorial representatives. Only private, non-farm, non-reserve and owner- or renter-households with incomes greater than zero and shelter-cost-to-income ratios less than 100% are assessed for 'core housing need.' Non-family households with at least one maintainer aged 15 to 29 attending school are considered not to be in 'core housing need' regardless of their housing circumstances. Attending school is considered a transitional phase, and low incomes earned by student households are viewed as being a temporary condition. 7 Military service status Military service status refers to whether or not the person is currently serving or has previously served in the Canadian military. Military service status is asked of all Canadians aged 17 and older. For the purposes of the 2021 Census, Canadian military service includes service with the Regular Force or Primary Reserve Force as an Officer or Non-Commissioned Member. It does not include service with the Cadets, Cadet Organizations Administration and Training Service (COATS) instructors or the Canadian Rangers. 8 Tenure refers to whether the household owns or rents their private dwelling. The private dwelling may be situated on rented or leased land or be part of a condominium. A household is considered to own their dwelling if some member of the household owns the dwelling even if it is not fully paid for, for example if there is a mortgage or some other claim on it. A household is considered to rent their dwelling if no member of the household owns the dwelling. A household is considered to rent that dwelling even if the dwelling is provided without cash rent or at a reduced rent, or if the dwelling is part of a cooperative. For historical and statutory reasons, shelter occupancy on Indian reserves or settlements does not lend itself to the usual classification by standard tenure categories. Therefore, a special category, 'dwelling provided by the local government, First Nation or Indian band,' has been created for census purposes. Presence of mortgage payments refers to whether an owner household makes regular mortgage or loan payments for their dwelling. Subsidized housing refers to whether a renter household lives in a dwelling that is subsidized. Subsidized housing includes rent geared to income, social housing, public housing, government-assisted housing, non-profit housing, rent supplements and housing allowances. 9 For more information on the military service status variable, including data quality and comparability with other sources of data, please refer to the Canadian Military Experience Reference Guide, Census of Population, 2021. 10 Adequacy, suitability, affordability and core housing need are four housing indicators. The indicator for housing adequacy is the dwelling condition. The indicator for housing suitability (a topic often referred to as crowding) is whether the dwelling has enough bedrooms for the size and composition of the household. The indicator of housing affordability is the proportion of household total income that is spent on shelter costs, also referred to as shelter-cost-to-income ratio. Core housing need refers to whether a private household's housing falls below at least one of the indicator thresholds for housing adequacy, affordability or suitability, and would have to spend 30% or more of its total before-tax income to pay the median rent of alternative local housing that is acceptable (attains all three housing indicator thresholds). 'Dwelling condition' refers to whether the dwelling is in need of repairs. This does not include desirable remodelling or additions. The category 'major repairs needed' includes dwellings needing major repairs such as dwellings with defective plumbing or electrical wiring and dwellings needing structural repairs to walls, floors or ceilings. 'Housing suitability' refers to whether a private household is living in suitable accommodations according to the National Occupancy Standard (NOS); that is, whether the dwelling has enough bedrooms for the size and composition of the household. A household is deemed to be living in suitable accommodations if its dwelling has enough bedrooms, as calculated using the NOS. Housing suitability and the National Occupancy Standard (NOS) on which it is based were developed by Canada Mortgage and Housing Corporation (CMHC) through consultations with provincial housing agencies. The category 'not suitable' includes households where the required number of bedrooms based on the NOS exceeds the reported number of bedrooms in the dwelling. 'Shelter-cost-to-income ratio' refers to the proportion of average total income of household which is spent on shelter costs. The category '30% or more of household income is spent on shelter costs' includes households who spend 30% or more of their average monthly total income on shelter costs. For more information, refer to the Census Dictionary: Dwelling condition; Housing suitability; Shelter-cost-to-income ratio; Core

In 2023, around 21.3 percent of active duty officers in the United States Navy were women. Additionally, approximately 19.4 percent of officers in the Space Force were women.

At the end of the fiscal year of 2024, it is estimated that there will be 15 Generals serving the United States Army, and a total of 354,948 enlisted personnel. Military personnel The military departments in the United States are: the U.S. Army, the U.S. Navy, the U.S. Air Force, the U.S. Marine Corps, and the U.S. Coast Guards. The President of the United States is the military’s overall head and forms the military policy with the U.S. Department of Defense. The U.S. military is one of the largest militaries in term of number of personnel.

The largest branch of the United States Armed Forces is the United States Army. The United States Army is responsible for land-based military operations. The active duty U.S. Army personnel number has decreased from 2010 to 2021. In 2010, there were 561,979 active duty U.S. Army members, as compared to 482,416 in 2021.

The number of active duty U.S. Navy personnel has decreased slowly over the past 20 years. In 2021, there were 343,223 active duty Navy members in the United States Navy. The United States Navy personnel are enlisted sailors, commissioned officers, and midshipmen. Sailors have to take part in Personnel Qualification Standards, to prove that they have mastered skills.

The United States Air Force is the aerial warfare service branch of the United States. The active duty U.S. Air Force personnel numbers also decreased between 1995 and 2015, although has started to increase slightly since 2015. The number decreased again in 2021, when the Air Force had 328,888 personnel.

In 2022, about 3.23 million veterans in the United States were male and between 35 and 54 years of age. In the same age group, about 627,148 females were veterans in that year.

The American Civil War is the conflict with the largest number of American military fatalities in history. In fact, the Civil War's death toll is comparable to all other major wars combined, the deadliest of which were the World Wars, which have a combined death toll of more than 520,000 American fatalities. The ongoing series of conflicts and interventions in the Middle East and North Africa, collectively referred to as the War on Terror in the west, has a combined death toll of more than 7,000 for the U.S. military since 2001. Other records In terms of the number of deaths per day, the American Civil War is still at the top, with an average of 425 deaths per day, while the First and Second World Wars have averages of roughly 100 and 200 fatalities per day respectively. Technically, the costliest battle in U.S. military history was the Battle of Elsenborn Ridge, which was a part of the Battle of the Bulge in the Second World War, and saw upwards of 5,000 deaths over 10 days. However, the Battle of Gettysburg had more military fatalities of American soldiers, with almost 3,200 Union deaths and over 3,900 Confederate deaths, giving a combined total of more than 7,000. The Battle of Antietam is viewed as the bloodiest day in American military history, with over 3,600 combined fatalities and almost 23,000 total casualties on September 17, 1862. Revised Civil War figures For more than a century, the total death toll of the American Civil War was generally accepted to be around 620,000, a number which was first proposed by Union historians William F. Fox and Thomas L. Livermore in 1888. This number was calculated by using enlistment figures, battle reports, and census data, however many prominent historians since then have thought the number should be higher. In 2011, historian J. David Hacker conducted further investigations and claimed that the number was closer to 750,000 (and possibly as high as 850,000). While many Civil War historians agree that this is possible, and even likely, obtaining consistently accurate figures has proven to be impossible until now; both sides were poor at keeping detailed records throughout the war, and much of the Confederacy's records were lost by the war's end. Many Confederate widows also did not register their husbands death with the authorities, as they would have then been ineligible for benefits.

In the fiscal year of 2024, the United States Navy estimates there will be a total year-end strength of 347,000 personnel. In the same year, they expect to have 10 Admirals and 32 Vice Admirals serving in the U.S. Navy.

The Navy

The United States Navy is the maritime branch of the U.S. Armed Forces, and is the largest navy int he world. In 2021, the Navy had around 343,223 personnel, and a budget of 162.9 billion U.S. dollars in the same year. Additionally, this branch of the Navy boats a large fleet of deployable battle force shops, totaling 285 in 2023.

Anchors aweigh

The number of active duty naval personnel has been on the decline in the U.S. since 1995, though the number of personnel has remained relatively steady since 2008. Among Navy officers in the U.S., there have historically been significantly more male officers than female officers.

In 2024, there were approximately 121,900 men in the armed forces of the United Kingdom, and 16,220 women. The reduction in personnel witnessed by the British Armed Forces in recent years is the result of a conscious attempt by the UK government to cut costs and modernize the military. This policy has been pursued since the 2010 Strategic Defence and Security Review, which among other things sought to replace many full-time regulars with reservists, and to end the UK’s permanent deployment in Germany. Cuts across air land and sea While the army has born the brunt of these cuts to personnel, all branches of the armed forces have also had to contend with the same issue. Since 2012, the Army has seen its personnel reduced by around 28,800, the RAF by 9,200, and the Navy by around 3,540 While the share of GDP spent on defense has not fallen quite as dramatically since 2012, over the long term, the UK has almost halved defense spending since the end of the Cold War. As of 2021, the UK spent 2.3 percent of GDP on defense, slightly above the minimum NATO requirement of two percent of GDP. Recent geopolitical events, such as the Russian invasion of Ukraine, have led to renewed calls for increased defence spending, with the current UK government aiming to spend 2.5 percent of GDP in the near future. Age of personnel In 2024, the average age across all ranks and branches in the UK armed forces was 31. This was the average age for all branches of the armed forces, except for the RAF, which had an average age of 33. During the same year, there were approximately 54,800 people in their 20s in the armed forces, compared with 45,410 in their 30s. Additionally, there were only around 7,760 people under the age of 20 in the armed forces, and just 90 aged 60 or over.

As of 2021, there were over 200,000 living United States veterans who served in the Second World War. The Department of Veteran Affairs projects that the number of living veterans will decline rapidly in the fifteen years until 2036, at which point just a few hundred Americans who served in the war will be still alive. The passing of the "Greatest Generation" is seen as symbolic by some, as for many people they represented the era when the United States' power on the world stage was at its greatest. The Second World war is particularly remembered as a "just" war in the U.S., as the United States was seen as fighting for democracy and self-determination, and against the tyrannies of Fascism, Nazism, and Japanese Imperialism.

The United States' involvement in the Second World War

World War II marked the peak in military enlistments in U.S. history, with over 16 million service members serving worldwide during the conflict. The U.S. joined the war in 1941 due to Imperial Japan's attack on the U.S. naval base at Pearl Harbor, Hawaii, before joining the European theater of the war in 1944 during the Invasion of Normandy. The U.S. military played a vital role in the defeat of Nazi Germany on the Western Front in May 1945, while the Soviet Red Army defeated the Wehrmacht in the East. The U.S. was also vital in the defeat of Fascist Italy, as they had led an allied invasion force onto the Italian peninsula from Northern Africa in September 1943. The final action of the war took place in the Asian theater of war, as Imperial Japan was the last of the Axis powers to concede defeat to the Allies. The United States effectively ended the war with the dropping of two nuclear bombs on Hiroshima and Nagasaki in August 1945, leading to as many as a quarter of a million deaths. It remains to this day the sole use of atomic weapons in an active conflict.

By 22034033, the number of military retirees in the United States is expected to reach 2.37 million; an increase from an estimated 2.27 million retirees in 2024. Military retirement pay In the U.S., military retirement refers to pension and benefit plans for those who have accumulated 20 or more years of active service. There are different factors that influence how much is paid out to different veterans, which includes length of service, disability percentage, the year the person entered the military, and type of retirement. The total payment for military retirees is expected to continue to increase, as well as their average benefits. However, the total outlays for the military retirement trust fund is expected to fluctuate, but ultimately rise over the next decade. U.S veterans The United States has one of the largest militaries in the world based on active personnel and has the largest defense budget in the world. However, many veterans in the U.S. struggle to find a job and find affordable housing when they return from deployment due to factors such as post-traumatic stress disorder and physical disabilities. The Department of Veteran Affairs seeks to help those coming back from training or combat assimilate back into everyday life.

In 2025, the lowest-ranking soldier in the South Korean military, the private second class, was paid 750,000 South Korean won per month. This was about half that of what a sergeant became. Military service in Korea Physically and psychologically healthy, South Korean men between the ages of 18 to 37 are required to serve mandatory military service for around 18 to 20 months. This mandatory service aims to ensure national security and defend against potential military threats from North Korea. Refusing compulsory military service can lead to legal consequences, although there are exemptions and alternatives. Defense industry in Korea The defense industry in South Korea has significantly grown in recent years and is also gaining more importance in the global defense market. South Korea is one of the top ten countries with the highest military spending. Additionally, the value of exports of the South Korean defense industry amounted to about 14 billion U.S. dollars. The country continues to invest in research and development (R&D) activities in the defense industry.

The First World War saw the mobilization of more than 65 million soldiers, and the deaths of almost 15 million soldiers and civilians combined. Approximately 8.8 million of these deaths were of military personnel, while six million civilians died as a direct result of the war; mostly through hunger, disease and genocide. The German army suffered the highest number of military losses, totaling at more than two million men. Turkey had the highest civilian death count, largely due to the mass extermination of Armenians, as well as Greeks and Assyrians. Varying estimates suggest that Russia may have suffered the highest number of military and total fatalities in the First World War. However, this is complicated by the subsequent Russian Civil War and Russia's total specific to the First World War remains unclear to this day.

Proportional deaths In 1914, Central and Eastern Europe was largely divided between the empires of Austria-Hungary, Germany and Russia, while the smaller Balkan states had only emerged in prior decades with the decline of the Ottoman Empire. For these reasons, the major powers in the east were able to mobilize millions of men from across their territories, as Britain and France did with their own overseas colonies, and were able to utilize their superior manpower to rotate and replace soldiers, whereas smaller nations did not have this luxury. For example, total military losses for Romania and Serbia are around 12 percent of Germany's total military losses; however, as a share of their total mobilized forces these countries lost roughly 33 percent of their armies, compared to Germany's 15 percent mortality rate. The average mortality rate of all deployed soldiers in the war was around 14 percent.

Unclarity in the totals Despite ending over a century ago, the total number of deaths resulting from the First World War remains unclear. The impact of the Influenza pandemic of 1918, as well as various classifications of when or why fatalities occurred, has resulted in varying totals with differences ranging in the millions. Parallel conflicts, particularly the Russian Civil War, have also made it extremely difficult to define which conflicts the fatalities should be attributed to. Since 2012, the totals given by Hirschfeld et al in Brill's Encyclopedia of the First World War have been viewed by many in the historical community as the most reliable figures on the subject.

China’s aircraft fleet is expected to reach an average age of 6.6 years in 2020, whereas the North American fleet an average age of 14 years. By 2030 this gap is expected to narrow though, with the average fleet ages predicted to be between 8.4 years and 14.1 years respectively.

Reasons for updating

The main reason for replacing aircraft is not because planes become less safe as they age, but because newer planes are cheaper to operate. For example, newer aircraft are generally more fuel efficient – an important factor given the volatility in the price of aircraft fuel and its current trend upwards. On average, aircraft are retired after around 25 years.

Fleet age trends

The general pattern is that more established markets and carriers have older fleets. For example, in the North American market, the traditional full-cost carriers have average fleet ages well above 10 years, whereas the average fleet age of the newer low-cost carriers are mostly below 10 years. However, established markets with a higher number of older aircraft provide more opportunity for aircraft to be replaced sooner. This explains the above forecast that the average fleet age in established markets will reduce by 2030, whereas markets with newer fleets will increase in average age.

In the past four centuries, the population of the United States has grown from a recorded 350 people around the Jamestown colony of Virginia in 1610, to an estimated 331 million people in 2020. The pre-colonization populations of the indigenous peoples of the Americas have proven difficult for historians to estimate, as their numbers decreased rapidly following the introduction of European diseases (namely smallpox, plague and influenza). Native Americans were also omitted from most censuses conducted before the twentieth century, therefore the actual population of what we now know as the United States would have been much higher than the official census data from before 1800, but it is unclear by how much. Population growth in the colonies throughout the eighteenth century has primarily been attributed to migration from the British Isles and the Transatlantic slave trade; however it is also difficult to assert the ethnic-makeup of the population in these years as accurate migration records were not kept until after the 1820s, at which point the importation of slaves had also been illegalized. Nineteenth century In the year 1800, it is estimated that the population across the present-day United States was around six million people, with the population in the 16 admitted states numbering at 5.3 million. Migration to the United States began to happen on a large scale in the mid-nineteenth century, with the first major waves coming from Ireland, Britain and Germany. In some aspects, this wave of mass migration balanced out the demographic impacts of the American Civil War, which was the deadliest war in U.S. history with approximately 620 thousand fatalities between 1861 and 1865. The civil war also resulted in the emancipation of around four million slaves across the south; many of whose ancestors would take part in the Great Northern Migration in the early 1900s, which saw around six million black Americans migrate away from the south in one of the largest demographic shifts in U.S. history. By the end of the nineteenth century, improvements in transport technology and increasing economic opportunities saw migration to the United States increase further, particularly from southern and Eastern Europe, and in the first decade of the 1900s the number of migrants to the U.S. exceeded one million people in some years. Twentieth and twenty-first century The U.S. population has grown steadily throughout the past 120 years, reaching one hundred million in the 1910s, two hundred million in the 1960s, and three hundred million in 2007. In the past century, the U.S. established itself as a global superpower, with the world's largest economy (by nominal GDP) and most powerful military. Involvement in foreign wars has resulted in over 620,000 further U.S. fatalities since the Civil War, and migration fell drastically during the World Wars and Great Depression; however the population continuously grew in these years as the total fertility rate remained above two births per woman, and life expectancy increased (except during the Spanish Flu pandemic of 1918).

Since the Second World War, Latin America has replaced Europe as the most common point of origin for migrants, with Hispanic populations growing rapidly across the south and border states. Because of this, the proportion of non-Hispanic whites, which has been the most dominant ethnicity in the U.S. since records began, has dropped more rapidly in recent decades. Ethnic minorities also have a much higher birth rate than non-Hispanic whites, further contributing to this decline, and the share of non-Hispanic whites is expected to fall below fifty percent of the U.S. population by the mid-2000s. In 2020, the United States has the third-largest population in the world (after China and India), and the population is expected to reach four hundred million in the 2050s.