"Due to growing income inequality, the share of earnings above the cap has risen from 10 percent in 1982 to over 16 percent in 2006. This is because incomes have grown strongly at the top while middle incomes have stagnated.
This trend is expected to continue, meaning that a growing share of earnings will remain outside the tax base.
The cap also means that higher-income individuals pay a smaller share of their income in Social Security taxes than middle-class employees. Including the employee and employer shares of Social Security and Medicare taxes, earners in the middle fifth of the income distribution pay an average effective payroll tax of about 11 percent. In contrast, the top 1 percent of earners pay just 1.5 percent on average.
Let me turn now to different options for making adjustments to the cap." (Piece of artical by John Irons)
Raising the social security tax cap, it should rise unilaterally with adjustments to inflationary costs. So, it has been studied over the past four years or better