In a remarkable illustration of the power of lobbying in Washington, a study released last week found that a single tax break in 2004 earned companies $220 for every dollar they spent on the issue — a 22,000 percent rate of return on their investment.

The study by researchers at the University of Kansas underscores the central reason that lobbying has become a $3 billion-a-year industry in Washington: It pays. The $787 billion stimulus act and major spending proposals have ratcheted up the lobbying frenzy further this year, even as President Obama and public-interest groups press for sharper restrictions on the practice.