Given the fact how high it surged in a comparatively short timeframe compared to overall human history. A Drop shouldn’t be unexpected.

Especially as lifestyles trend towards increasingly unhealthy and we are routinely around and consuming increasingly more chemicals then we were even 20 years ago. Some studies increasingly link various food additives to increasing health problems.

Obesity is rising as we have increasingly sedentary lives. Which means all the health issues associated with being fat come with that and push down overall numbers.

Various new health conditions, allergies and other issues have been periodically cropping up. Really since the 40s to 50s. Which further affect numbers.

The Amount of sleep you get plays a role in your overall health and therefore life expectancy. Having an irregular sleep schedule long term can affect every aspect of your health negatively .

As does stress level. With both insomnia and excessive stress becoming increasingly prevalent issues particularly in American society.

One also shouldn’t forget that life expectancy also factors in violent crime rates, drug use/Over doses, suicides, and a myriad of other factors.

Frankly it’s a surprise it hasn’t dropped sooner. Given the rising health issues. Rising Crime rates, Surging Suicide rates, and ever present and steadily worsening drug problems.