By Ross Benes

Commissioner Adam Silver recently discussed tweaking the NBA lottery system, since right now there's just too much perceived incentive for teams to tank. Emphasis on favoring tomorrow over today was evident during Thursday's trade deadline as teams like the 76ers were willing to provide others with cap relief in exchange for future draft picks.

And it's not just the Sixers who are neglecting their current roster to "rebuild" for the future. What stands out most, even more so than the Warriors' and Hawks' dominance, is how many really bad teams there are this season (especially in the East). To see just how abnormal this is, and how that's affecting parity, we examined the amount of sub .400 teams each year since the ABA-NBA merger, using Basketball-Reference data.

There are many ways to judge what makes a team bad. A sub .400 winning percentage seemed reasonable as a cutoff, because you'd be hard pressed to find a team that wins fewer than 40 percent of its games and isn't terrible. But more than just measuring the amount of bad teams, we wanted to see how this relates to parity, since the amount of parity in a league affects how exciting and watchable the season is.

To measure this, we looked at each season's average standard deviation in winning percentage and point differentials. While this is just a rough look that doesn't capture all the potential various nuances of parity, a standard deviation at least lets us know when teams are veering far away from the mean on average. While a low standard deviation would show more consistency and less disparity.

The sortable table below shows how each season ranks in their percentage of sub .400 teams and their standard deviations of winning percentages and point differentials.  

Year Sub. 400% STDWL STDPD
1991 0.370 0.158 5.142
2015 0.367 0.179 5.179
1986 0.348 0.144 4.306
1994 0.333 0.177 5.416
2012 0.333 0.156 4.811
2010 0.333 0.163 4.704
1997 0.310 0.191 5.466
2001 0.310 0.157 4.494
1983 0.304 0.161 4.822
2013 0.300 0.155 4.607
1995 0.296 0.161 5.036
1992 0.296 0.159 5.018
1990 0.296 0.174 4.940
1989 0.280 0.162 5.570
1998 0.276 0.189 5.514
1996 0.276 0.171 5.292
2000 0.276 0.161 4.775
1999 0.276 0.159 4.511
1979 0.273 0.103 3.415
1978 0.273 0.111 2.971
2008 0.267 0.169 5.517
2009 0.267 0.172 4.781
2014 0.267 0.158 4.741
2011 0.267 0.161 4.723
1987 0.261 0.151 4.855
1988 0.261 0.157 4.850
1981 0.261 0.161 4.449
1985 0.261 0.146 4.158
2003 0.241 0.144 4.274
2002 0.241 0.144 4.274
2007 0.233 0.132 3.865
1980 0.227 0.152 4.142
1993 0.222 0.158 5.069
1982 0.217 0.153 4.096
1984 0.217 0.115 3.280
2004 0.207 0.136 3.942
2005 0.200 0.155 4.144
1977 0.182 0.098 3.155
2006 0.167 0.136 3.851

As seen in the table, this season has the second highest percentage of teams that win less than 40 percent of their games -- only 1991 ranks higher. Since the merger, on average there have been 27.2 percent of teams with a sub .400 record each season. This year is nearly ten percentage points (which equates to two standard deviations) above the mean.

Given this season's surplus of bad teams, it makes sense this season has the third highest variance in winning percentage. Only 1997 and 1998 rank higher, which has less to do with the bottom and more to do with the top of the league during those years. In both 1997 and 1998, the Bulls and Jazz both won more than 75 percent of their games each season. And in 1998, there were five teams that finished with a plus .700 record. (The relationship between the amount of bad teams and parity isn't perfect. But we did find a significant correlation, r=0.58, between a year's rank in sub .400 teams and rank in winning percentage variance.)

One brighter note for this season is that the point differentials aren't as historically out of sync. This season ranks seventh in point differential variance. In the second half of the season, records might regress to the mean and mirror these victory margins. But even then, this year could end up as one of the least competitive overall when you look at the entire league from top to bottom.

The excessive amount of terrible NBA teams is actually pretty similar to what we saw in the NFL this season. The perception of the NFL as an "Any Given Sunday" league of parity was already a bit mythological before this season. And it's been common to see a mere handful of players dominate the NBA finals for the majority of a decade. But what's alarming is the NBA and NFL are simultaneously creating a humongous division between their haves and have nots as their amount of awful teams have increased. This leaves MLB, the only major sport (hockey and soccer aren't major sports in America) without a salary cap, as the only league putting together something resembling unpredictability and parity.

Is it any wonder, then, why teams like the Sixers continue to bargain away the now in exchange for the future? It's a matter of simple math.

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Ross Benes is a Sports on Earth contributor who has written for Deadspin, The Wall Street Journal, Esquire and Slate. You can reach him at rossbenes@gmail.com and follow him on Twitter @RossBenes.