BlackRock Chief Executive Officer Laurence Fink last month called for a savings program, most likely a mandatory one, to supplement Social Security to provide for longer life spans.

“We need to make the retirement crisis our No. 1 national priority and pursue a comprehensive solution that allows people at all income levels to benefit from being investors,” said Fink, head of the largest money manager in the world with more than $3.5 trillion in assets, writing in an op-ed piece in Politico.

Fink said the need for increased retirement resources has become more acute because Americans are living longer––the average 65-year-old will live for two more decades and one out of every four will live past 90. He added that while the pool of retirees is getting bigger, the base of workers to support them with payments to Social Security is getting smaller.

Fink contrasted Social Security payments and private investment returns to explain why Social Security supplemented with a savings plan is needed. A worker who contributed the maximum to Social Security would get $28,000 a year beginning at 65, Fink said, but if he and his employer had contributed the same amount beginning when the worker was 30 to a diversified portfolio, the guaranteed income after 35 years would be $42,000.