From the USATODAY:
Although the new Yankee Stadium has the identical dimensions as its predecessor, it has yielded 87 home runs, the most ever in a ballpark's first 23 games, according to the Elias Sports Bureau. There were 46 home runs hit through the same number of games last year at the old Yankee Stadium located across the street.
There have been nine games in which at least five home runs were hit. In three other games, teams have combined to hit seven or more. All told, the new stadium is on pace for 306 home runs, which would surpass the record 303 hit in 1999 at Coors Field in Denver. Last year, 160 home runs were hit at the old stadium.
Home run inflation at new Yankee Stadium pumps debate - USATODAY.com