Apple's (AAPL) share in the worldwide smartphone operating system market posted a year-over-year decline to 13.2% during the second quarter of 2013, according to a report published by IDC. Google's (GOOG) Android maintained its leadership position with 79.3% share, while Microsoft's (MSFT) Windows Phone posted the largest year-over-year increase among the top five smartphone platforms, moving up to 3.7% share, IDC said. BlackBerry (BBRY) saw its OS market share decline to 2.9% during the quarter, reaching levels not seen in the history of IDC's Mobile Phone Tracker. According to IDC, vendors shipped a total of 236.4M smartphones in Q2, up 51.3% from the 156.2M units shipped in the same quarter of last year. Second-quarter shipments grew 9.3% when compared to Q1.