# The Zodiac, Congress, and probability...

A blog I sometimes frequent had a letter sent to it that noted that, for some bizarre reason, the Washington Post has a way to sort Congressional votes based on the Congresscritter’s astrological sign.

Doing so reveals something mildly interesting: of the 432 members of Congress, an oddly high number (55) are Cancers, as opposed to only 24 Tauruses.

According to the blog, there aren’t enough births in the Cancer months over the other signs to account for this large a difference. Barring the obvious jokes about Cancer and Congress, how likely is such a distribution, probability-wise, assuming that this is just a random occurrance? Can anyone think of any factor that might have nudged things towards this result?

If you keep looking for statistical anomalies, the odds that you’ll eventually find one approach 100% very quickly.

People with Cancer as their astrological sign were born in July and August. Therefore they never had the experience growing up of having a birthday celebration during the school year and having a day when they were awarded special recognition as an individual. This lack of attention led them to overcompensate and seek out careers in politics so they could experience the feeling on election day that they were being singled out for recognition by the crowd.

That, or it’s a statistical fluke.

Only 35 are Cancers, so I presume you misread the table. In any case, there’s a standard way to look at the number of items in a set of categories and tell how probable that distribution is. It’s called a chi-square test. Do you want us to try that test and see how random this distribution is?

35 Cancers voted “yes,” 17 votes “no,” and 3 did not vote. 55 total.

Ooh, I do! I love chi-squared tests. At what level of confidence can you reject the null hypothesis of a random distribution?

Sorry, I guess I misread the table. So the table gives the following numbers of members of the House of Representatives (Note: just of the House, not the whole Congress) with each astrological sign:

Aquarius 36
Aries 30
Cancer 55
Capricorn 34
Gemini 47
Leo 32
Libra 43
Pisces 26
Sagittarius 27
Scorpio 30
Taurus 24
Virgo 48
Total 432

There are actually 435 members of the House, so three members haven’t been listed for some reason. Are there unfilled seats at the moment? Anyway, 432 divided by 12 is 36, so the average number of House members per sign is 36. For a chi-square test, you square the deviations from the mean and add them and then divide by the average value. That gives:

(02 + 62 + 192 + 22 + 112 + 42 + 72 + 102 + 92 + 62 + 122 + 122) / 36 = 30.33

A chi-square value of 30.33 for 11 degrees of freedom (Note: the number of degees of freedom is the number of categories minus 1) has a probablity of .0014, according to the online calculator where I just looked this up. That’s certainly a little odd. I wonder if the number of Representatives for each astrological sign was miscounted?

Are births in the general American population even uniformly distributed throughout the calendar year? I doubt it.

I’d like to see a graphic of some kind that shows the exact dates of the birthdays, rather than just the signs. Both for the population in general, and for the representatives.

That’s pretty significant, assuming the data check out okay, I slept through learning chi-square. It would be interesting to explain the differences, although I am not quite ready to blame it on the zodiac. Maybe there were higher conception rates around September, accounting for high Gemini and Cancer rates, for example.

It seems there are two vacancies in the House (link). If so, that website isn’t accounting for one member. They seem to be missing a Republican.

Horoscopes are bunk as far as I’m concerned, yet I can’t help feeling a little… amused? that I share my birthsign with the fewest Representatives.

I haven’t done a thorough search, but this table shows Canadian births by month. Note that it is by no means even. There are notably fewer births Nov-Feb.

Also, if you look through other years using the site referenced by the OP, Congress is not always as skewed, suggesting that the particular congressional makeup referred by the OP is an anomaly.

Just because the probability that an event happened by chance is low doesn’t mean that it didn’t happen by chance. It’d be interesting to see stats for the house since its inception; it may be that the current distribution of birth signs is just noise and the overall distribution is closer to uniform.

You’ve no idea how much the universe conspires to make that true. You see, my third-grade teacher decided to have a birthday event for all the kids with summer birthdays. It was to be in the afternoon. On that day, I broke my femur in morning recess and I ended up spending months in a hospital bed. (Medical technology has advanced since then, fortunately.)

So, are you going to tell us your real name, so we know that we’re electing a Doper to Congress?

When the time comes, I’ll be sure to let you know.

My calculations are only accurate if you assume that the number of people born in each astrological sign is about the same. If that’s not true, I would have to be given the proportion born in each sign so that I could recalculate the figures. Does anyone have the proportions born in each sign? More importantly, would someone look up the birthdays of all the present members of Congress and calculate the number born under each sign? (Try The Almanac of American Politics.) I don’t trust the calculations of this article.

Here’s an interesting chart, based on Austrian data (so it may or may not say anything about US births - I haven’t found a similar US chart yet). It shows that moderately and highly educated people are more often born in the spring, and averagely educated people in the fall. “We … calculated the seasonal distribution of the birth dates of Austrians aged 50+ by educational group on the basis of the 1991 census.” Whole article.

One might assume that senators would fall into the higher education line, which does show the largest range in deviation. I don’t know if it’s statistically significant or not.

Cancers are summer babies - right between 6 and 7 on the graph, where it starts to fall off precipitously, Virgos (the next largest represented sign) in the 7-8 range, even lower. If senators were to come from the red line, we’d expect most of them to be Arieses and Tauruses, which are actually the two LOWEST represented signs. So something’s fishy here, and it may be my assumption that we have similar birth patterns to Austrians, or that senators are highly educated.

Remember that the signs do not correspond with the months - they go from the late middle of one month to the middle of another, usually switching around the 21st or so.

Found this site, which claims that in the Encyclopeadia Brittanica, people with a career in “politics” are least likely to be Cancers, and most likely to be Libras or Aquariuses. (Which is in agreement with what an astrologer might say: given similarity in the rest of the chart, a Libra will be more likely interested in justice and maintaining social equilibrium, and Aquariuses seek out “causes” and fight social injustice.)

Make of it what you will. I don’t vouch for the site, although the purpose of it is to examine Astrology through the lens of statistics.

You could also sort members of Congress by sex, religion, skin colour, wealth and sexual orientation.
I’m prepared to take a guess that male, white, wealthy, straight Protestants are in the majority.
Unlike horoscopes, this does tell us something!

Here are the Vital Statistics of the United States from 1945, which I’m hoping will be a reasonably representative birth year for members of Congress. Natality by month is shown at the bottom right of Page XX. The pattern of births by month is somewhat consistent from year to year, but not completely, so any choice of base year is going to be arbitrary.

Nevertheless, I used the 1945 figures to recalculate the expected number of members by sign. I made the further simplifying assumption of converting signs to months based on the larger fraction of the month; in other words, Capricorn is equivalent to January, even though it really runs from December 21 to January 21 or thereabouts. (Sources don’t always agree on the exact dates.)

My new expected number of Reps per sign is: Cap 36.6, Aqu 36.8, Pis 35.8, Aries 34.4, Tau 34.4, Gem 36.0, Can 37.3, Leo 37.7, Virgo 37.9, Lib 35.8, Scor 34.9, Sag 34.4.

My new chi-squared statistic is 24.47, significantly smaller than the previous value of 30.33.