NLP on NPR’s Commencement Addresses

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Vocativ did an interesting analysis of the President’s State of the Union (SOTU)
. They showed that across the past couple hundred years and
many Presidents, SOTU speeches have been targeted at audiences with
lower and lower education levels.

Vocativ’s in-print interpretation of the downward sloping trend was that a speeches have gotten
less sophisticated. Their recommended share-tweet for the article was more blunt:

We think there could be another interpretation, a growing populist bent in US culture that
influenced even how POTUS did the SOTU.


Tyler and I wanted to test for that broad cultural influence in other formal
addresses. But what other kinds of speeches happen as regularly and
consistently as SOTU? And then it struck us: commencement speeches! And
what better test?

If commencement speeches are always targeted at an on-average relatively more
educated audience of college graduates (and their families), then if we
still see the same trend in language, this would be a fairly decent test
that a cultural shift was influencing public address in general.

In the following series of posts, I’ll share the methods, data, and
insights we found. We not only replicate Vocativ’s analysis, we extend
it in several interesting ways, using different types of text analysis
and a view inspired views of the data.


Commencing with Commencements.

Since the Vocativ article uses a common grade-level readability formula
to measure the education level of the audience, all we really needed was
to scrape some commencement addresses and apply the same readability
algorithm. Also, we thought we’d extend the methodology by using several
readability measures averaged together for robustness.


Luckily for us, NPR had built a great web app to collect as many
commencement addresses as they
could readily find: 350+ speeches, in fact. So, with a bit of
BeautifulSoup code (more on that to come!), we were able to scrape the
website for many of the cool insights that data and portal afford.

First Results

But not to leave you hanging until our next post: when we compare our
results (first graph above) to the interactive visualization that Vocativ produced, we do in
fact find the same relative downward trend among the 280 usable
speeches, from 12th grade level in the 1950s to 8th grade level in 2014.
In this time series plot, we aggregate speeches by year, and scatter
their occurrence with a trend line and bivariate correlation measure.

The negative time trend is not proof-positive of the populist
interpretation, as opposed to a more curmudgeonly view on American
education; but it is at least a stronger test than the original on new
data and independent contexts. Finding the same results generalize
across these instances, pretty much exactly, does say something for the
populist interpretation.

The Code

We provide the code and data to reproduce the longitudinal readability
graph below. The data provided is the output from the readability
function in the GitHub readability package, not the raw text (we
intend to release the full text based data set at the end of the blog

Load Packages & Data

if (!require('pacman')) install.packages("pacman")
pacman::p_load_gh("trinker/syllable", "trinker/readability")
pacman::p_load(dplyr, qdap, ggplot2, RCurl, readr, foreign)

## read in readability data
readability_scores_by_id_year <-
"" %>%
    getURL() %>%
    textConnection() %>% 
    read.csv() %>% 

The output shows the speech id, year, 5 readability scores
(Flesch Kincaid,
Gunning Fog Index,
Coleman Liau,
SMOG, & Automated Readability Index), and
an aggregate readability score. (Vocativ uses the first of the above
five scores.) Readability scores are generally, computed from a
combination of simple counts and ratios of a of characters, syllables,
words, and sentences. The gist is that complex words and sentences make
the comprehension of these texts more difficult.

Munging and Visualizing

To interpret the data we created the changes in speech readability over
time visualization
, using an aggregate of average grade level
readability scores. Below, the dplyr & ggplot packages make
light work of the data munging and plotting task.

readability_scores_by_id_year %>%
    group_by(Year) %>%
        Readability = mean(Average_Grade_Level),
        n = n()
    ) %>%
    ggplot() +
        geom_smooth(aes(x=Year, y=Readability), fill=NA, size=1,
            method='lm', color='blue') +
        geom_point(aes(x=Year, y=Readability, size=n), alpha=.3) + 
        geom_point(aes(x=Year, y=Readability), size=1) +
        scale_size_continuous(range = c(3,10), name='N Speeches') +
        theme_bw() +
            panel.border = element_blank(), 
            axis.line = element_line(color="grey50") 
        ) +
            expand = c(.01, 0), 
            limits = c(1955, 2015), 
            breaks = seq(1955, 2015, by=5)
        ) +
        ggtitle('Average Yearly Readabilitynof Speeches Over Time') +
        annotate('text', x = 1962, y = 10.7, 
            label = 'italic(r[xy] == -.299)', 
            parse = TRUE, color='blue'
        ylab('Grade Level')

To Come in Future Posts

Next we hope to post about choices we made for scraping websites:
specifically, how Python’s BeautifulSoup faired and what it was like to
run the project on Jupyter/iPython Notebook vs an IDE.

In the meanwhile, go check out Tyler’s readability package and github star it for doing such a great job. Follow the button below.


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