No Market Share movement for Drupal Version 5.1x yet sorry.
Get a list of 834 websites using Drupal Version 5.1x which includes location information, hosting data, contact details, 157 currently live websites
and an additional 46 domains that redirect to sites in this list. 677 sites that used this technology previously and 71 websites in the United States currently using Drupal Version 5.1x.
Distribution of locations of all Drupal Version 5.1x customers we've ever tracked.