According to researchers at Rentrak, video-on-demand has witnessed exceptional growth in 2011, the fastest of any alternative TV platform, climbing 17 per cent and reaching 8.8 billion transactions. Of these transactions, free content (free-on-demand) accounted for 6.8 billion, and is now the top category, up from third place last year. According to Rentrak, "the potential value of the ad inventory in these programs is at least $1 billion."