Just under one third of US digital music downloads come from just 50 songs

"On 6/27/10, the 2010 YTD Digital Tracks Current chart showed the Top 50 songs totaled 69,608,330.
On 6/27/10, the National Sales Summary (Track) chart showed that YTD, there were 231,863,000 current tracks sold YTD."
Source:  Data from Nielsen Soundscan, reported by DigitalMusicNews, 7th October 2010