[aothman]

Study author here.

You can think of the AngelList investment data as being split into three roughly equal-sized groups: markdowns, markups, and no valuation updates.

The reported IRRs are actually relatively high and the return multiples (which are compounded IRRs) are relatively low. That's because there are lots of one- and two-year-old companies in the dataset and---as we show---IRRs and investment durations are negatively correlated.