Honestly a mental swag. To put actual numbers in it, life expectancy was 20 years, now 80 years.

That means roughly 0.9% chance a of death per year now, vs 3.4% ancestrally. Thats 73% of deaths avoided per year. I think that compounds year over year since those people who would otherwise have did are also alive to avoid more deaths.

So, even at the indisputable low end… 73%.