Checking MathSciNet in the five-year period from 2010 to 2014, there were 1319 entries with "erratum" or "errata" in the title. Sampling a few dozen of them, most cases involve a misstatement severe enough to affect the statement of a theorem. In a few cases, something was inadvertently left out, such as MATLAB code or an author's name. For perspective, during this period, there were 525795 items added to MathSciNet.