Tax Foundation:  Tax Equity and the Growth in Nonpayers:

• In 2010, 41% of all tax returns filed had no income tax liability. This represents over 58 million income tax filers.
• Nonpayers have grown substantially over the last two decades. In 1990, only about 21 percent of returns had no tax liability, about half of what it is today.
• The expansion of tax credits is the primary driver of the increased number of nonpayers. The budgetary cost of tax credits reached $224 billion in 2010.
• Though most nonpayers of the income tax are generally low income, the number of nonpayers in middle income categories has grown. The median income of nonpayers has increased by 40% over the last 9 years.
• The threshold at which a typical married couple with two children will likely be a nonpayer is now $47,000.