Jimmy Carter, who turned 100 today and is the longest-lived U.S. president in history, holds another, less noticed distinction: He’s the most prolific author of any president in a century. Mr. Carter has written or co-written 32 books in his lifetime, 20 of which became New York Times best sellers.

But that expansive literary legacy has a flip side. Just 16 books written by others that prominently deal with Mr. Carter or his administration have made the best-seller list, a stark contrast to the dozens of volumes lavished on every other modern president.

The result is a striking fact: Mr. Carter, who remains in hospice care, was in many ways a president who had a lot more to say than has been said about him.

That ratio — best sellers written by a president before, during and after his presidency versus best sellers written about him — can be calculated for commanders in chief going back to 1931, when The Times first began tracking hardcover nonfiction book sales. Doing so reveals a few patterns.

The clearest lesson is that while Americans like to read and write about their presidents, they don’t read or write about all of them equally. Nor is every president equally inclined to leave a legacy measured in volumes.