Please visit https://www.theeffectbook.net to read The Effect online for free, or find links to purchase a physical copy or ebook.
The Effect is a book about research design and causal inference. How can we use data to learn about the world? How can we answer questions about whether X causes Y even if we can't run a randomized experiment? The book covers these things and plenty more. These videos are meant to accompany the book, although they can also be viewed on their own.
This video relates to material found in Chapter 18 of the book.
A version of this video without background music can be found here: https://youtu.be/V6NUeVwHxC4
It's the most commonly-used research design in observational causal inference! Difference-in-differences is a pretty simple idea that can be applied any time you have a treatment that went into effect at a particular time, but it only applied to some groups and not others. How does it work? This video explains.