The guys over at the AVS Forum and other boards like High Def Digest have been pulling together sales data from Nielson Videoscan and other sources to try and come up with a consolidated estimate for weekly Blu-ray and HD-DVD sales.

Since the start of the year, Blu-ray has maintained a rough 2-to-1 sales advantage over HD-DVD. As mentioned on other threads, Blu-ray has built this advantage because of its larger studio support and installed user base.

For the week of 3/11, Blu-ray outsold HD-DVD by a margin of 4-to-1. This is interesting because neither format had any new titles that week, and while the estimated unit sales represented a major dropoff from the week before, it seems that HD-DVD had a much sharper sales decline. Keep in mind that this trend occurred before the release of Casino Royale, which is a Blu-ray exclusive and the biggest concurrent new release for either HD disc format since the November release of Superman Returns. Given that the Blu-ray version of Casino Royale peaked at #8 on Amazon's sales chart (1st HD title to break into the top 10), and HD-DVD won't see any new releases until March 27th, I would expect this gap to widen considerably over the next couple of weeks.

Last week's sales data will be available by next Monday, so it will be interesting to see how wide a margin Blu-ray builds up before HD-DVD gets back into the game with new releases of its own starting on March 27.