The 100-Win Cubs and Competitive Balance in MLB

In today's article on ESPN about the 100-win Cubs, David Schoenfield writes, "(W)e’ve had more parity in the past decade, making 95- and 100-win seasons increasingly rare." He measures this by comparing the number of teams with 95+ wins since MLB expanded to 30 teams in 1998:

1998-2006: 44 teams with 95-plus wins

2007-2016: 33 teams with 95-plus wins

I sought to see if a more mathematical calculation of competitive balance (CB) backs this up. I've looked at CB in the NBA in the past, and I applied this same technique to MLB (since 1998) by calculating the Noll-Scully Measure (NSM), which is the ratio of the actual standard deviation in each to season to the "ideal" standard deviation for that season. The lower the NSM, the greater CB there is in the league, with a perfectly balanced league having a ratio of 1.

In the two periods Schoenfiled indicated, there is indeed a difference in the NSM: it is much higher from 1998-2006, which implies less competitive balance.

1998-2006: 1.95 average NSM

2007-2016: 1.72 average NSM

For perspective, this season it is currently 1.724, which is right in line with the last decade, an era of more parity.