Ratings for the season finale of Fox's onetime summer powerhouse So You Think You Can Dance dropped 13 percent from last year Thursday night. The first hour of the two-hour special averaged fewer than 6 million viewers, placing third among total viewers and tying for second among viewers 18-49. The second hour averaged 6.8 million viewers, placing second. Still, those figures were up 24 percent over last week's installment. The big winner for the night was CBS's long-running Big Brother , which rounded up 8.64 million viewers.