Ideally, you'd check the proportions starting from something like mathematical success or career intent in high school. Then you move on to college majors, graduation rates, and applicant pools. This is really important, because otherwise you end up focusing energy on non-leaky parts of the pipeline and achieving nothing.

This article focuses on interviewing, but the segment on black colleges and office siting is crucial. Ensuring unbiased interviews doesn't stop you from drawing interview candidates from disproportionately white colleges. Holding local code-ins won't save you from having offices in overwhelmingly white cities. "Lowering the bar", which companies are (according to this) hugely concerned about, still wouldn't solve the problem.

If you're studying the mismatch between 13% of the population and 1% of your workforce, the numbers you want are the ones that show where things went wrong.