Is 150 Million Gallons a Lot? It Depends.

A question from my Twitter feed:

Does this stat seem plausible? The existence of—allowing people to compare mileage and operating costs of different vehicles—has reduced US petroleum consumption by over 1 billion gallons since 1999? Not bad for a website, if so.
— brad plumer (@bradplumer) October 31, 2019

Well, we use about 150 billion gallons of gasoline per year and the linked presentation says that has reduced consumption by about 150 million gallons per year. That’s 0.1 percent. So sure, that seems plausible. But then again, I could probably womp up a case that practically anything you care to name has a 0.1 percent effect on anything else you could name. Go ahead and test me.