* Invasions due to overextension as far as territory to defend
== Roman Empire population decline and China's population decline/China's demographic crisis ==
'''Roman Empire population decline:'''
[[File:Roman empire population decline.png|thumbnail|center|800px|[https://www.google.com/search?q=roman+empire+falling+population&oq=roman+empire+falling+population&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIICAEQABgWGB4yDQgCEAAYhgMYgAQYigUyDQgDEAAYhgMYgAQYigUyDQgEEAAYhgMYgAQYigUyCggFEAAYgAQYogQyBwgGEAAY7wUyBggHEC4YQNIBCTExMDEzajBqMagCALACAA&sourceid=chrome&ie=UTF-8 Roman Empire population decline] ]]
'''China's population decline/China's demographic crisis:'''
[[File:China's demographic crisis.png|center|600px|[https://www.google.com/search?q=does+china+have+a+demographic+crisis&oq=Does+China+have+a+demographic+crisis&gs_lcrp=EgZjaHJvbWUqBwgAEAAYgAQyBwgAEAAYgAQyCAgBEAAYFhgeMggIAhAAGBYYHjIICAMQABgWGB4yCAgEEAAYFhgeMg0IBRAAGIYDGIAEGIoFMg0IBhAAGIYDGIAEGIoFMgoIBxAAGIAEGKIEMgYICBAuGEDSAQkxNzAzMWowajGoAgCwAgA&sourceid=chrome&ie=UTF-8 Does China have a demographic crisis?] ]]
'''Articles:'''
According to ''Forbes'' magazine, as far as the fertility rate of China: "...the Total Fertility Rate (births per woman) dropped in 2021 to just 1.15, far below the 2.1 required for a stable population."<ref>[https://www.forbes.com/sites/franklavin/2022/10/12/chinas-demographics-it-gets-worse/?sh=6102ba4331d1 China’s Demographics: It Gets Worse], Forbes magazine, Oct 12, 2022</ref> In 2022, the historian [[Niall Ferguson]] indicated that [[China]]'s population is projected to drop by 50-75% by the end of the century.<ref>[https://www.youtube.com/watch?v=Q2vqnpXWM0Y&t=601s Niall Ferguson on the projected drop of China's population in the 21st century]</ref>
'''Videos:'''
*[https://www.youtube.com/watch?v=y4qbjd4I_c0 China's demographic catastrophe: Could half the population disappear?], Center for Eastern Studies, 2024
*[https://www.youtube.com/watch?v=kBMSZ7v3KxQ New Chinese Demographic Data = Population Collapse], 2024
*[https://www.youtube.com/watch?v=cekVVi2EiJ8 Why China’s Demographic Crisis Just Keeps Getting Worse], TLDR News Global, 2023
== Roman Empire and nomadic invasions. China and its modern wars ==
