An interesting analysis from Vocativ:
President Obama’s 2015 State of the Union address was written for a tenth-grader, which makes it the most high-minded of all his SOTU speeches, a data analysis by Vocativ reveals. Generally, in order for Obama to make himself understood to the broadest possible swath of the population, he tailors his speeches to the intellect of a 14-year-old. But over the last few years the grade level of the president’s speeches has edged up. Vocativ analyzed all of Obama’s SOTU addresses using the Flesch-Kincaid readability test—the most widely recognized reading comprehension algorithm—and gave each speech a numerical grade. Roughly speaking, the spectrum begins at first grade and goes up from there, corresponding to elementary, middle and high school, and then to college and graduate school.
Hit the link for an infographic on SOTU addresses going back to Woodrow Wilson.