The first All-Star Game was in 1933. Ever since, the Midsummer Classic has provided a convenient, if mathematically inaccurate, way of dividing the baseball season into halves. The first “half” has comprised, over the last 10 years, an average of 90 games. The remaining 72 games of the schedule make up the second “half.” I’ll dispense with the quotation marks here, but keep in mind this is a figurative, not literal, half.

This year, the All-Star Game was a little earlier than average, so the first half was a little shorter than average, with the 30 clubs playing between 87 (Baltimore, Boston, and Milwaukee) and 91 (Dodgers, Toronto) games, with an average of 89. Through Labor Day, teams had played an average of 48 games in the second half, with an average of 25 games to go.

And wouldn’t you know it, we’re seeing something that we’ve never seen before.

Generally, teams’ records in the second half are similar to their records in the first half. There are trades and injuries, players get hot and cold, schedules get harder and easier, but generally, the teams are the same. Good teams stay good. Bad teams stay bad. Mediocre teams stay mediocre.

From 1933 to 2015, there were 1,894 team-seasons. During that period, the correlation between teams’ first-half winning percentage and their second-half winning percentage was 0.56. Since the start of divisional play in 1969, it’s 0.49. Since the start of the wild card era in 1995, it’s still 0.49. This falls squarely in the range of what statisticians designate as a moderate correlation. That’s unsurprising; while we don’t expect teams to have the exact same winning percentage in the first and second halves of the year (though that’s happened 12 times, most recently last season’s Orioles, who played exactly .500 ball in both the first and second halves), we expect them to be close. Over half of teams have had a second-half winning percentage within 60 points of their first-half winning percentage. That means for a team going 45-45 prior to the All-Star break, odds are that it’ll win 36 games, plus or minus four, after the break. That’s not a big difference.

But that’s not to say there haven’t been big differences. At the top of the chart is the 1977 Phillies. They were terrible in the first half of the year, going 24-61, by far the worst record in baseball, but they were 44-33 after the All-Star break. Their 68-94 record was good for only fifth place in the six-team NL East, but the improvement in their winning percentage from .282 in the first half to .571 in the second is best since the first All-Star game. Here are the 10 teams that improved the most from the first half of the season to the second:

First Half Second Half Final Year Team W L Pct Place W L Pct Diff Place 1997 Phillies 24 61 .282 6 44 33 .571 .289 5 1935 Browns 19 50 .275 8 46 37 .554 .279 7 2001 A's 44 43 .506 2 58 17 .773 .268 2 1940 Cardinals 27 40 .403 6 57 29 .663 .260 3 1979 Dodgers 36 57 .387 6 43 26 .623 .236 3 1995 Mets 25 44 .362 4 44 31 .587 .224 2 1944 Tigers 36 42 .462 7 52 24 .684 .223 2 2005 Devil Rays 28 61 .315 5 39 34 .534 .220 5 2000 Astros 30 57 .345 6 42 33 .560 .215 4 1936 Dodgers 24 50 .324 8 43 37 .538 .213 7

By and large, these aren’t good teams. Only three finished above .500. The 1944 Tigers finished a game behind the Browns, and the 2001 A’s had 102 wins but were 14 games behind the 116-46 Mariners. The best that could be said about the rest is that they dug themselves too big a hole in the first half of the year to overcome.

By contrast, the teams that fell off the most in the second half are a bit of a different story. Some were bad teams that got worse. But most had winning records in the first half of the year. Through the end of last season, of the 10 teams that had the largest decline from the first half to the second, all but two were above .500 in the first half of the year. The 1977 Cubs were in first, 54-35, 2.5 games ahead of the Phillies in the NL East, but suffered the second-greatest relative collapse in history, going 27-46 after the All-Star break, to finish fourth. The 2001 Twins were in first in the AL Central, 55-32, five up on the Indians, but had the third-greatest decline, 30-45, to finish second. The 1951 White Sox were in first in the American League, 49-29, a game ahead of Boston and two ahead of New York, but had the 10th-greatest tumble, 32-44, to finish fourth, 17 behind.

However, the preceding paragraph is under review. The magnitude of the first-to-second half declines by the Cubs, Twins, and White Sox may have to be subject to a one position increment. Because 2016 has brought a solid contender for the biggest decline in winning percentage from the first half of the year to the second:

First Half Second Half Final Year Team W L Pct Place W L Pct Diff Place 2016 Giants 57 33 .633 1 16 31 .340 -.293 ? 1943 A's 34 44 .436 8 15 61 .197 -.239 8 1977 Cubs 54 35 .607 1 27 46 .370 -.237 4 2001 Twins 55 32 .632 1 30 45 .400 -.232 2 2004 Brewers 45 41 .523 4 22 53 .293 -.230 6 1975 Brewers 46 42 .523 3 22 52 .297 -.225 5 1949 Senators 33 42 .440 6 17 62 .215 -.225 8 1941 Indians 46 31 .597 2 29 48 .377 -.221 4 1995 Tigers 37 33 .529 2 23 51 .311 -.218 4 1940 Giants 40 28 .588 3 32 52 .381 -.207 6

As you can see, it’s not particularly close. At the All-Star break, the Giants had the best record in baseball, three games better than the Cubs. Winners of four straight games and eight of their previous 10, they had a 6.5-game lead over the Dodgers. They had the whole even-numbered-year thing going.

Since the break, though, the story’s reversed. San Francisco lost six in a row after the break and 11 of 13. They had two separate four-game losing streaks in August. Since the All Star break, the Giants have the worst record* in baseball, 1.5 games worse than the Twins. They’ve vaulted to the no. 1 position for the biggest second-half decline in winning percentage, passing, among others, the wartime 1943 Philadelphia Athletics, who finished 49-105. With 25 games remaining after Labor Day, the Giants need to win at least 13 in order to avoid becoming the team with the worst difference in winning percentage from the first to the second half of the season in baseball history.

Even if it isn’t really a half.

*All records through Monday.