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An exercise in decluttering

My friend Xan found the following chart by Pew hard to understand. Why is the chart so taxing to look at? 

Pew_collegeadmissions

It's packing too much.

I first notice the shaded areas. Shading usually signifies "look here". On this chart, the shading is highlighting the least important part of the data. Since the top line shows applicants and the bottom line admitted students, the shaded gap displays the rejections.

The numbers printed on the chart are growth rates but they confusingly do not sync with the slopes of the lines because the vertical axis plots absolute numbers, not rates. 

Pew_collegeadmissions_growthThe vertical axis presents the total number of applicants, and the total number of admitted students, in each "bucket" of colleges, grouped by their admission rate in 2017. On the right, I drew in two lines, both growth rates of 100%, from 500K to 1 million, and from 1 to 2 million. The slopes are not the same even though the rates of growth are.

Therefore, the growth rates printed on the chart must be read as extraneous data unrelated to other parts of the chart. Attempts to connect those rates to the slopes of the corresponding lines are frustrated.

Another lurking factor is the unequal sizes of the buckets of colleges. There are fewer than 10 colleges in the most selective bucket, and over 300 colleges in the largest bucket. We are unable to interpret properly the total number of applicants (or admissions). The quantity of applications in a bucket depends not just on the popularity of the colleges but also the number of colleges in each bucket.

The solution isn't to resize the buckets but to select a more appropriate metric: the number of applicants per enrolled student. The most selective colleges are attracting about 20 applicants per enrolled student while the least selective colleges (those that accept almost everyone) are getting 4 applicants per enrolled student, in 2017.

As the following chart shows, the number of applicants has doubled across the board in 15 years. This raises an intriguing question: why would a college that accepts pretty much all applicants need more applicants than enrolled students?

Redo_pewcollegeadmissions

Depending on whether you are a school administrator or a student, a virtuous (or vicious) cycle has been realized. For the top four most selective groups of colleges, they have been able to progressively attract more applicants. Since class size did not expand appreciably, more applicants result in ever-lower admit rate. Lower admit rate reduces the chance of getting admitted, which causes prospective students to apply to even more colleges, which further suppresses admit rate. 

 

 

 

Comments

derek

The original chart swooped up and to the right, but I think your decluttered version would look better swooping down and to the right, the better to visually support the statement "applications doubled but admit rate halved."

Kaiser

derek: I see that the labels created confusion. I was trying to stick to "selectivity" as a measure rather than admit rate because I actually want the most selective colleges on top of the chart, not at the bottom. So the vertical axis is inverted.

Jeff Weir

Re your question "why would a college that accepts pretty much all applicants need more applicants than enrolled students?"

'Need' is probably the wrong term. 'Get' is probably a better one. Perhaps it's just getting easier to apply. I routinely apply for far more jobs than I used to 15 years ago, because technology (mainly the 'mainstreaming' of email) has lowered the cost to me of applying. Could that be the case here, in part? And the other part perhaps being application processes themselves have become less onerous (particularly for the less selective schools)?

Kaiser

JW: One other factor I used thought of is that the less selective schools probably don't charge application fees so that further lowers the barrier to applying.

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