"This direct effect of growing inequality accounts for far more than half of the gap in Social Security’s finances, but there is also a very important indirect effect. In 1960, the Social Security tax rate was 6.0 percent, combining the employer and employee side contributions. By 1990, the tax rate had risen to 12.4 percent, an increase of 6.4 percentage points over 30 years. In the last 35 years, the tax rate has not increased at all."