Baseball’s ERA+ stat

I like baseball’s ERA+ stat. It gives you a way to compare completely different eras in a logical way. In technology it’s like saying which feat is better, creating a huge website like Facebook, or creating the first versions of Unix or Mac OS? All of them are great feats of engineering, but the tools available in each generation are so different that there’s no way to compare them, but in baseball the ERA+ stats lets you do exactly that.