This chart from Jon Roegele of The Hardball Times shows the MLB strike zone for right-handed hitters has expanded 46 square inches since 2009. And this season had the largest single-year increase of the PITCHf/x era as the zone grew 16 square inches expanding from 459 square inches to 475.
Roegele examined PITCHf/x data for every one-inch square above home plate. Each spot where strikes were called more often than balls was included in the strike zone. He found the low part of the zone keeps growing and right-handed batters now have a strike zone 17 square inches larger than lefty zones on average.
Baseball's expanding strike zone has been well documented. From 2008 to 2013, it grew 23 square inches. What's incredible is it still continues to expand. Read the rest of Roegele's analysis over at The Hardball Times.