As widely reported by CNN, the Huffington Post, Talking Points Memo, the sophistication of speeches by US politicians has declined in recent years, dropping from an 11th-grade level in 2005 to a 10th-grade level today. The reports are based on an analysis by the Sunlight Foundation, based on textual analysis of congressional speeches given since 1996 provided by the Capitol Words API. You can see where your favourite legislator ranks in this table. Picking out a couple of famous names, Sen. Rand Paul (R-KY) ranks near the bottom with an 8th-grade speaking level; near the top of the ranks is retiring senator Olympia-Snowe (R-ME) who speaks at a Grade 14 level.
A regression analysis detailed in the article teases out some of the contributing factors. While the speech levels of members of both parties have declined over the past couple of years, the chart below shows that for Republicans, the more ideological extreme the congressperson, the less sophisticated the speech.
It's clear that the data visualizations were created using R's ggplot2 package; presumably the statistical analyses were peformed with the R language as well. For the infographic circulated to the media, the ggplot2 charts have been cleaned up using an editing tool like Illustrator (easy if you export the chart to PDF from R).
Read the details of the analysis in the full report from the Sunlight Foundation linked below.
Sunlight Foundation: The changing complexity of congressional speech