Low wages aren't the only reason that the poor are getting poorer and the richer are getting richer.

According to new research from the Economic Policy Institute, high-income Americans are 10 times more likely to have retirement accounts than those at the low-end of the income spectrum. And, the national shift away from defined-benefit pension plans into 401(k)'s has left more and more older Americans retiring in poverty.

In the richest nation on the planet, this is simply unacceptable. That's why EPI and other organizations are pushing Congress to expand – not cut – Social Security benefits.

Decades ago, most working-class Americans were able to retire with dignity because of the defined-benefit plans provided by their employers, but that's no longer the case. Those plans were pretty much wiped out and replaced with 401(k) plans that may or may not include matched contributions from employers.

As low-wage workers don't have much to contribute, employers don't match anything, and retiring workers end up with little-to-no savings when it comes time to leave the workforce. And, even if some workers were able to save, their savings were subject to the turns of the stock market.

Wealthier workers were able to contribute and save more in their retirement plans, and they are often better able to withstand the ups and downs of the market. The income disparity in retirement savings is so pronounced, 74 percent of total savings in retirement accounts belongs to the top 20 percent of earners, even though that group only brings in 63 percent of all income.

Rich people aren't just earning more, they're saving more, and that leaves them in better shape for retirement. Poor people are left with no choice but to rely on Social Security benefits, which leaves them living in poverty.

We can and should do better, and that starts with expanding, not cutting, these important benefits on which so many rely.