This is the third installment in my “Fun with Congressional Data” series in which I’ll take a look at the percent of Republicans and Democrats after midterm elections. Previously, I took a look at the majority party in congress and it’s connection to GDP and a look at what congressmen did prior to being elected. The data again, comes from here. First let’s take a look at the proportion of each party as a whole of congress over the years since 1857. I’m starting in 1857, since that marked the beginning of the two party system between Democrats and Republicans.

Out of the 80 congressional elections during this time, democrats won a congressional majority 44 times (55%) compared to 35 for Republicans. They tied once. One of the trends that we note is that when a party has a substantial margin for a number of years in congress, that proportion doesn’t flip quickly. Rather they go back towards 50%. Here are the 5-number-summaries of the samples for the two proportions:

summary(DemPCT)

Min. 1st Qu. Median Mean 3rd Qu. Max.

23.05 44.65 52.42 50.82 58.86 76.84

> summary(RepPCT)

Min. 1st Qu. Median Mean 3rd Qu. Max.

19.96 40.89 46.61 47.84 53.76 76.95

So you can see that Republicans had both the lowest and highest percentages of congress, in 1939 and 1865, respectively. These represent two vastly different time periods in American History, the end of the civil war and the beginning of World War 2 (also during FDR’s presidency). Now let’s take a look at the breakdown in the Senate.

In the senate, we see the same trend that the country tends to go back to the middle, rather than flipping extremes in parties. The five-number-summaries are shown below:

summary(DemPCT)

Min. 1st Qu. Median Mean 3rd Qu. Max.

14.86 44.04 48.96 48.59 56.68 78.12

> summary(RepPCT)

Min. 1st Qu. Median Mean 3rd Qu. Max.

17.71 42.00 50.00 49.53 55.00 82.43

In this case, Democrats had the lowest proportion of senators out of all years in 1969 while republicans had the highest held percentage of the Senate during this time. Finally, let’s shift our focus to the House of Representatives below:

The house data is more fickle than the senate (and overall congressional data) with one 10% or more majorities by a party turning into a 10% minority in between elections. The election for the congress starting in 1875 in which a 69.28 % republican majority turned into a 36.52 % minority. Democrats held a majority for 43/80 of these congresses. The final 5-number-summary for this data are shown below:

summary(DemPCT1)

Min. 1st Qu. Median Mean 3rd Qu. Max.

23.60 44.27 52.71 51.39 59.43 76.55

> summary(RepPCT1)

Min. 1st Qu. Median Mean 3rd Qu. Max.

20.46 40.18 46.56 47.40 54.48 75.92

Here we see that Republicans had the lowest percentage in the congress that started in 1937, the same year that Democrats had their highest proportion of representatives.

But what about independents?

We’ll get to that next week! So tune in next week for:

“The Myth of Independent Representation and 2016 Choices”

If you enjoyed this post, check out the previous “fun with congressional data” posts.

Till next week!

-Andrew G. Chapple