By James Hibberd
July 01, 2011 at 04:38 PM EDT

Only a few summers ago, Fox’s So You Think You Can Dance was unstoppable in the ratings, strong enough for the network to give the reality competition a run during the ultra-competitive fall.

This summer, bolstered by the return of judge Mary Murphy, the show debuted as strong as ever with its most-watched premiere in four years — 9.1 million viewers and a 3.2 adult demo rating. Since, the show has dropped sharply and Thursday’s episode hit an all-time summer low — 5 million viewers and 1.6 rating, down 20 percent from last week.

Some fans say the show is as great as ever this season. Could it just be the show’s age? But then why was the premiere so high? More likely, most of the biggest drops occurred after SYTYCD‘s Wednesday edition faced NBC’s The Voice the past couple weeks, though last night’s show certainly didn’t have any unique competition. That we’re approaching the holiday weekend likely didn’t help either…

Anyway: The second week of ABC’s Expedition Impossible (6.1 million, 1.8) took a knock too, down 25 percent. Wipeout (6.5 million, 1.9) was down 21 percent and Rookie Blue (5.4 million, 1.4) was down 13 percent.