The complexities also go well beyond the nuances of benefit-taking decisions that armies of salesmen offering free dinners are eager to help us make. [...] the more you earn, the more likely some aspects of Social Security will irk you. Built into the crediting formula for retirement benefits, the tax is far steeper than the taxes we pay on current income. The intent was to provide a retirement income backup system for all Americans. Fortunate workers who earn more than $4,917 monthly pay six times as much in taxes on higher earnings to get the same increase in retirement benefits as a low-wage earner receives. [...] Social Security isn't as progressive as it seems for a simple reason: [...] as I've pointed out in other columns, the life expectancy difference between people with high earnings and people with low earnings is growing. [...] one study revealed that women with less than a high school education lost four years of life expectancy in a recent 20-year period. Examining years of survival after age 55 by income decile, the researchers found major differences in life expectancy.