http://www.hardballtimes.com/are-umpires-racist/
Which refutes the earlier HBT article. The conclusion is that there is really no discernable bias....
And a great quote from the article:
If there is bias is it a big deal?
Not really. Guy, commenting at Baseball Think Factory made the following observation:
For example, a black pitcher gets the call 30.62% of the time, with these racial “disparities”: W Ump: 30.61, H ump: 30.77, B Ump: 30.76. So, if a black pitcher was judged by a same-race (black) ump 91% of the time (as white pitchers now are), he would gain one extra called strike for every 784 called pitches. A starter has about 50 called pitches per start, so a black starter might get 2 more strike calls in a season. Let’s be generous and say that results in 1 fewer walk (or 1 more K) each year (it’s probably less than that), in which case he would give up 1 additional run every 3 years or so.
Steady as she goes,
moe