As the 2016 season reaches the three-quarter mark, which teams have made the greatest strides since last year? We can answer that question based on a comparison of winning percentages from the final records for 2015 and the current standings.
This measurement won't do much for the Cardinals, who won 100 games last year, or the Pirates, who won 98, although it won't stop the Cubs, who won 97. But it will give us a solid handle on which clubs have the most impressive upward mobility, in this case the top two teams in each division.
American League East
Boston Red Sox
2015 win pct.: .481
2016 win pct.: .558
Gain: +.77
Baltimore Orioles
2015 win pct.: 500
2016 win pct.: .558
Gain: +.58
Two of the most dynamic offenses in the game battle with the Blue Jays for the top of this division, while hoping that they can get enough pitching to put them over the top. Boston leads the Majors in runs scored, while Baltimore leads in home runs. Impressive strides have been taken, particularly by the Red Sox, who are attempting another worst-to-first journey.

AL Central
Cleveland Indians
2015 win pct.: .503
2016 win pct.: .580
Gain: +.77
Detroit Tigers
2015 win pct.: .460
2016 win pct.: .529
Gain: +.69
Cleveland has the AL's second-best team ERA. The Tribe has the kind of pitching that can succeed in the postseason. Detroit, closer to full health in the second half, has been putting together a combination of a powerful offense and quality starting pitching.

AL West
Seattle Mariners
2015 win pct.: .469
2016 win pct.: .533
Gain: +.64
Texas Rangers
2015 win pct.: .543
2016 win pct.: .590
Gain: +.47
Seattle has the third-best team ERA in the AL, and enough hitting to put itself within sight of Texas and squarely in the middle of the AL Wild Card race. The Rangers have triumphed over injury and adversity. They look extremely astute with their acquisition of catcher Jonathan Lucroy, who is helping them offensively, defensively and in handling the pitching staff.

National League East
Washington Nationals
2015 win pct.: .512
2016 win pct.: .592
Gain: +.80
Philadelphia Phillies
2015 win pct.: .389
2016 win pct.: .467
Gain: +.78
Washington is playing back up to its potential with Dusty Baker managing. The Nats have the second-best team ERA in the Majors. A down season from Bryce Harper has caused more curiosity than damage. Congratulations to the rebuilding Phils for making the leap from eminently beatable to highly competitive in the short span of one season.

NL Central
Chicago Cubs
2015 win pct.: .599
2016 win pct.: .642
Gain: +.43
Cincinnati Reds
2015 win pct.: .395
2016 win pct.: .425
Gain: +.30
It is difficult to improve from a 97-victory season, but this is what Chicago is doing with the best record in the Majors. Can this be the Cubs' year? You just have to stay tuned. It is the only way. The rebuilding Reds have been playing better in the second half, even after the trade of power-hitting Jay Bruce.

NL West
Colorado Rockies
2015 win pct.: .420
2016 win pct.: .479
Gain: +.59
San Francisco Giants
2015 win pct.: .519
2016 win pct.: .554
Gain: +.35
OK, there has been some underachievement occurring in this division, but you have to give Colorado credit for moving up from last to third. San Francisco, in an even-numbered year, had the NL's best record at the All-Star break, but now is in a Wild Card position. The Dodgers aren't on this list, but they've been playing without Clayton Kershaw and they're back in first place, so that should count in their favor.

Nothing is definitively decided in mid-August, but all 12 teams on this list of the clearly improved have every right to feel better about themselves than they did at the end of last season. That is a foundation. That is progress.