According to Nielsen Media Research and Adams Media Research, the total high-def software sales for the first 2 years are only half of what standard DVD sales were for their first 2 years. There were 16.3 mln standard DVDs sold in the first two years (1997-1998) and there have been only 8.3 mln high-definition (both Blu-Ray and HD DVD) units sold in their first two years (2006-2007).