We know this partly also because when countries introduced mandatory birth registration, there was a sudden drop in people who lived beyond 100 years old. Here's a paper from earlier this year on this:
Between 2001-2021, the Veteran Affairs Disability Compensation payments in the US quadrupled
Based on quasi-random assignment of recruits to units the paper finds deployment can't explain the rise in disability payments, which is more likely driven by policy changes. The Economist published an article about this today, linking the issue also with conversations around efficiency in public spending:
>"The biggest shift over the past two decades has been an ever-expanding list of “presumptive conditions”—ailments that are assumed to be service-related without requiring proof. This list now includes common afflictions such as asthma, chronic rhinitis and type-2 diabetes. Once on the payroll, veterans rarely leave it and can pile on new claims indefinitely. Many start with minor conditions such as sleep apnea, and stack on additional diagnoses until they reach the maximum payout... Research shows disability payments have markedly reduced employment among veterans, and delivered no measurable improvement to their mental or physical health."
"What caused the end of antiquity, the shift of economic activity away from the Mediterranean towards northern Europe? [...] Our estimates suggest that reduced trade openness arising from the cost of crossing the newly formed border between Christianity and Islam, combined with technical progress and increased minting output in Muslim Spain and in the Frankish lands, explains the increased urbanization of western and northern Europe relative to the eastern Mediterranean from the 8th to the 10th century."
