The five most improved NBA offenses - and five that have plummeted

Here's a chart of how every team's offensive efficiency has changed from 2012-13 to 2013-14, as measured by points scored per 100 possessions. (Through the games of Jan 16. Thanks to NBA.com/stats for the data.) The five teams in green have shown the most improvement, while the five in orange have decreased efficiency the most. The NBA average is in purple.

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Looking at the 5 most improved:

1. Blazers: Thanks to Wesley Matthews, Damian Lillard and Nicolas Batum, Portland is second in the NBA in both 3-point attempts and percentage. No one else is hitting more than 10 threes a game. And no other team is hitting 82% of their free throws either.
2. Suns: Phoenix had the 2nd-worst offense in the league last year. Now they're in the top ten. How? Losing Michael Beasley helped (a lot). So did spacing the floor with at least 3 shooters all the time. Gerald Green, Eric Bledsoe, Goran Dragic, Channing Frye and Marcus Morris are each taking at least three 3PA per game - and each is hitting at least 35%. Kudos to Jeff Hornacek.
3. Timberwolves: A healthy Kevin Love. Kevin Martin doing K-Mart things. Nikola Pekovic bruising people inside (53% FG). It's a dynamic offense that also doesn't give away possessions (3rd-lowest turnover rate in the NBA).
4. Wizards: The worst offense in the league last season (and especially brutal without John Wall), Washington is now just slightly below-average. When healthy, they're big, athletic, and can space the floor juuuust enough to succeed.
5. Mavericks: Dirk Nowitzki is back to being his hyper-efficient self. Monta Ellis played out of his mind for the first two months. And Jose Calderon is hitting 47% of his threes. Yowza.

And the 5 teams that have plummeted the most on offense:

1. Knicks: Last year, New York led the league by a mile in 3PA, and had the 5th-best 3p%. This year they're 8th in attempts and 17th in percentage from downtown. So they must be trying to make it up inside, right? Nope: dead last in free throw attempts and 22nd in 2P%. This offense has to be elite to compensate for the Knicks' myriad issues on defense. Right now, it's not even leaue-average.
2. Bucks: Wait, is Milwaukee actually missing Brandon Jennings? I don't know if I'd go that far... except that their three highest-usage players (Brandon Knight, O.J. Mayo and Gary Neal) are shooting a combined 41% on all two-pointers. The guards don't get the ball to John Henson and Giannis Antetokounmpo enough, and the entire team avoids the free-throw line like the plague. Yet somehow, even with that overall passivity, the Bucks have the 5th-highest turnover rate in the league. Also, Gary Neal is one of your three highest-usage players??
3. Lakers: First, without Dwight Howard and Kobe Bryant, the Lakers have cratered in offensive rebounding (13th last year, 26th this year) and getting to the line (2nd last year, 14th this time). These are both symptoms of the bigger issue: every possession is a struggle to get a quality shot.
4. Thunder: Turns out it's hard to sustain the most efficient offense in the NBA without Russell Westbrook. And with Kendrick Perkins. And Thabo Sefolosha forgetting how to shoot.
5. Jazz: Given that 5 of the top 6 Jazz players in minutes played are 23 or younger, ranking 23rd in offensive efficiency isn't bad. (The league-worst defense, on the other hand...)