Though video-on-demand penetration has been growing, its TV usage share seems to have leveled off and may even be decreasing, according to a report last week by Nielsen Media Research, writes MediaPost. VOD ratings have grown 600 percent since Nielsen began tracking it: up from a 0.03 percent of U.S. TV usage in September 2003 to 0.21 percent in December 2005, the most recent month it has reported. That's down from last summer's 0.23 percent of U.S. TV usage.

The Nielsen report says much of the gain in the national VOD rating over the past 28 months can be "attributed to increased accessibility, but the increased and improved program offerings were likely a contributing factor."

It also suggests that VOD is a factor in certain dayparts (such as late night and prime-time), during certain days of the week and among specific demographics (especially children and young adults). The highest VOD rating - 0.16 - is among adults 18-34 watching late-night weekday programming; next is among persons 12-17 in prime-time; and Kids 2-11 averaged a 0.11 rating during prime access.