Most notable among the magazines’ top 20 was perennial #1 (since 1991) People falling short of both its 2010 record and the $1 billion mark. The decline likely worsened in the first quarter with People’s ad pages -8.3%.On the flip side, Bloomberg Businessweek’s +29.4% ad revenues put it in the top 20 for the first time since the early-2000s, when the subsequent technology advertising collapse and recession led to McGraw-Hill Cos. ending its 80-yearownership with the October 2009 sale to Bloomberg L.P., which renamed and overhauled BW with much fanfare and success. Bloomberg BW’s +8.4% ad-page first quarter suggests continuation. The momentum should also continue for Vogue. Its+13.8% ad revenues were second best to Bloomberg BW in the top 20, and ad pages through April were +2.15%…