WASHINGTON (CBS) — A government transparency group has analyzed the speeches of members of Congress, and ranked them at grade levels.

As WBBM Newsradio’s Bernie Tafoya reports, the analysis was conducted by the Washington, D.C.-based Sunlight Foundation. Overall, it found that Congress collectively speaks at a 10.6 grade level – or that of a high school sophomore – compared with that of a high school junior in 2010.

LISTEN: WBBM Newsradio’s Bernie Tafoya reports

By comparison, the average American reads only at an 8th- or 9th-grade level, according to the foundation. But the U.S. Constitution is written at a 17.8-grade level – apparently the level of a student almost a full year into a master’s or professional degree program – and the Declaration of Independence is written at a 15.1-grade level, or that of a college junior.

In the Illinois Congressional delegation, Rep. Danny Davis (D-Ill.), with his stentorian pronouncements, is rated the highest, with speeches at the college sophomore level. Tea Party Rep. Joe Walsh (R-Ill.) gets the bottom grade, with speeches on the order of only a high school freshman.

Speeches for the Illinois delegation as a whole are at the high school junior level.

The best-spoken member of Congress in the study is Rep. Daniel Lungren (R-Calif.), who speaks at a college senior level. The worst is Rep. John Mulvaney (R-S.C.), who only speaks at a 7th-grade level.

A summary of the report suggested that Congress is getting dumber, but said some people will see it as Congress communicating more effectively.

The analyses of the Congressional speeches use the Flesch-Kincaid test, which equates higher grade levels to longer words and sentences.