Low-income Americans are dying younger compared to their higher-income peers, hence losing out on earned Social Security benefits, according to a new study prepared for Sen. Bernie Sanders by the Government Accountability Office.

The life expectancy disparity between the rich and poor has eroded the progressive effect of Social Security, the report shows. American men earning about $20,000 a year expect to lose 11-14 percent of their lifetime Social Security benefits, while men earning about $80,000 a year expect to see their benefits increase as much as 16-18 percent due to their longer life expectancy, according to the report.

“Poverty should not be a death sentence,” Sanders, the ranking member of the Primary Health and Retirement Security Subcommittee, tweeted.

“Today, the wealthiest Americans contribute less to Social Security than at any other time in recent history," Sanders said. "We must reject calls to raise the retirement age and instead strengthen Social Security by ensuring millionaires and billionaires pay their fair share.”

The Vermont senator has made inequality and expanding Social Security centerpieces of his presidential campaign, noting that income gains over the past three decades have gone to those earning above the $118,500 earnings cap and have therefore been exempt from Social Security taxes, costing the Social Security Trust Fund over $1.1 trillion.

Read the report.