The Average Umpire Is Almost 50. The Best Ones Might Be in Their 30s. - WSJ
Two wrongs trying to make a right – makeup calls are common for MLB umpires, financial analysts and probably you - Boise State News
Why are MLB umpires so bad at calling inside pitches as strikes when they should be balls? - Quora
What is a strike in baseball? Robots, rule book and umpires view it differently
Best of BP: The Philosophy of Robot Umps and Hit By Pitches - Baseball ProspectusBaseball Prospectus
MLB Umpires Missed 34,294 Pitch Calls in 2018. Time for Robo-umps?, BU Today
Petition · Remove Angel Hernandez - The Worst MLB Umpire ·
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Why it's time for Marlins to demote Jacob Stallings - Fish Stripes
Rockies Mailbag: Is Bill Schmidt's draft record a concern? Is pitch framing out of control?
Baseball Umpires Make a Surprising Amount of Errors on Gameday, Study Shows
Analysis of nearly 4M pitches shows how many mistakes umpires make - Boston Business Journal