Bluebulb Projects' The Measure of Things presents:
13 is about three times the number of Living U.S. Presidents.
In other words, the count of Living U.S. Presidents is 0.30 times that amount.
(a.k.a. Presidents of the United States; a.k.a. Presidents of the United States of America; a.k.a. POTUS), (2016 figures) (including current)