What would cause Update Statistics with FULLSCAN to run slower when hitting auto created _WA statistics for the same table? For example, we have a table with 233,310,864 records. When running Update Statistics with FULLSCAN and then querying sys.stats I can see the four user created indexes (one clustered and three non-clustered) get updated in approximately 5 minutes per index. The 14 auto created column statistics (_WA) take approximately 22 minutes each. I'm guessing this has something to do with an internal algorithm used by SQL Server during update statistics, but I would love to hear an explanation for this performance difference.