A growing trend of almost venomous partisanship among U.S. elected officials may be responsible for more than an obstructionist Congress -- it also could be lowering the standards of congressional speech-making in the hallowed halls of the U.S. Senate and House and Representatives.

Americans elected to Congress are becoming increasingly plainspoken, according to a new analysis by the open government group the Sunlight Foundation. The average grade level at which members of Congress speak has fallen by almost a full grade since 2005, found the report, which noted the younger, most partisan members of both parties tended to speak with less sophistication than their older counterparts.

Today, members of Congress speak at about a 10.6 grade level, down from 11.5 in 2005. Meaning, they've dropped from junior to high school sophomore levels.

While the score represents the first time the quality of congressional speech has actually been recorded as plummeting, the Sunlight Foundation reports lawmakers from both parties still speak with more complexity than the average American. Of course, it's worth noting that it's actually extremely difficult to gauge the reading ability of typical Americans; a much-cited 1993 study from the U.S. Department of Education placed it somewhere between an eighth and ninth grade level.

How Speech is Graded

To come to its conclusion the Sunlight Foundation analyzed the entire Congressional Record -- which documents every word members of Congress say on the floor of the House or Senate -- from 1996 to the present day. The group plugged the record into a searchable database and then used an algorithm to analyze the speeches using the Flesch-Kincaid test, which equates high grade levels with longer sentences and words with more syllables.

We just kind of did it for fun, and I was kind of shocked when I plotted that data and I saw that, oh my God, there's been a real dropoff in the last several years, Lee Drutman, a political scientist at the Sunlight Foundation, told NPR of the grade-level drop since 2005.

Members of Congress currently speak at the level of a high school sophomore.  By comparison, Drutman points out the U.S. Constitution -- when measured by the same Flesch-Kincaid test -- is written at about a 17.8 grade level, beyond a four-year college degree, while the Gettysburg Address comes in at a 11.2 grade level and Martin Luther King, Jr.'s I Have a Dream speech is at a freshman -- 9.4 -- grade level.

The Highest and Lowest Scoring Members of Congress

Rep. Daniel Lungren, R-Calif., was judged to have the highest grade ranking among members of both the upper and lower chambers. An example of one his sentences, highlighted by NPR, is demonstrative of the syntax, vocabulary and sentence length associated with a higher Flesch-Kincaid score.

That 62-word sentence: This Justice Department, in my judgment, based on the experience I've had here in this Congress, 18 years, my years as the chief legal officer of the state of California and 35 or 40 years as a practicing attorney tells me this administration has fundamentally failed in its obligation to attempt to faithfully carry out the laws of the United States.

Lungren, who has held his seat since 2005, was determined to speak at about a 16 grade level.

He was followed by: Rep. Lucille Roybal-Allard, D-Calif., at a 14.9 grade level; Rep. Jim Gerlach, R-Pa., at 14.19; Rep. Thomas Petri, R-Wis., at 14.19; Sen. Daniel Akaka, D-Hawaii at 14.18 and Rep. William Thornberry, R-Texas, at 14.13.

On the opposite end of the spectrum, Rep. John Mick Mulvaney, R-S.C., had the lowest career grade level among members of the House and Senate at 7.95.

An example of Mulvaney's speech: I thought that Paul [Rep. Paul Ryan] and the leadership negotiated in good faith. They gave us some of the things we asked for. They didn't give us everything we asked for, but that's the nature of negotiation.

That's three sentences, averaging out to about 10.1 words per sentence.

Mulvaney assumed office in January 2011. He was followed by: Rep. Rob Woodall, R-Ga., who scored a 8.02 grade level; Sen. Rand Paul, R-Ky., at 8.04; Rep. Sean Duffy, R-Wis., at 8.09; Rep. Tim Griffin, R-Ark., at 8.13 and Rep. Todd Akin, R-Mo., at 8.14.

Partisanship Among Junior Members Associated With Lower Score

Those touting political extremes, especially those on the far right, usually had the most simple speech patterns. The trend is particularly visible among the newest members of Congress, who may have learned to condense their speeches into neat talking points easily digestible for YouTube and the cable news cycle.

Among members who have held their seats for under three years, lawmakers' speech patterns became increasingly simplified as they moved to either extreme of the political spectrum, according to a Sunlight Foundation scatterplot tracking partisanship (as determined by voting data) and speech sophistication.

The grade level of Congressional Record speeches declines most among Republicans as their voting record becomes more conservative. The drop from the most moderate to most conservative lawmakers is, on average, almost three whole grade levels, from 13th (colllege freshman) to 10th grade.

While the scatterplot did not reveal a similar relationship between grade level and ideology among Democrats, the organization reports junior members of that party who tend to vote with its most liberal faction usually had lower grade levels.

The correlation between partisanship and speech complexity is a relatively new trend. Among lawmakers who have held their seats for 11 to 20 years, the pattern on the right (more conservative, simpler speech) remains, but reverses on the left, where there is a link between liberalism and a higher speech grade level.

However, Republicans win -- at least for speech complexity -- in the end. Among members of Congress who have held their seats for 20 years or more, Republicans speak, on average, at a higher level than Democrats. There is only the vaguest link between conservatism and simple speech among Republican lawmakers in that group.