Favorites keep winning, but number of perfect March Madness brackets keeps getting smaller

The pursuit of the perfect NCAA Tournament bracket continues, but for far fewer people than when Saturday’s second-round games tipped off.

By Saturday evening, after wins by top seeds Duke and Michigan and third-seeded Michigan State, the number of unblemished entries had dropped to 105 in ESPN’s bracket challenge and 133 in the NCAA’s contest. There were more than 25 million entries in each.

Favorites went 16-0 on Friday, and they started 3-0 on Saturday. Duke, picked to win the...