Going through a funnel (a pyramid chart)

It's rare that you see a pyramid chart that is actually created dynamically. For the most part, they're designed and fleshed out creatively and turn into a .jpg file when they reach the web, and that's exactly why I wanted to start this chapter with this chart—it's not as complex as it might sound.

A pyramid chart is in essence a way for us to visualize changes in data that are quantitative by nature. They have a clear relationship between the lower layers and the higher layers. That sounded very vague, so let's explain it through an example.

Imagine that X amount of people complete their eighth year of school in a given year, if we follow the same group of people, how many of them would have completed their twelfth year of education four years later? Fair enough! We can't know the answer to that, but one thing we do know is that it can't be more than the initial X amount of people. The idea of a pyramid chart is exactly that of a body of data, of which...