As Major League Baseball reached the exaggerated benchmark of July 4 this week, the season had produced some intriguing developments. Which of these are the most impressive and least expected?

• The Pirates in first place in the National League Central with the best won-lost record in majors (52-31).
• The Red Sox, who finished last last season, leading the American League East most of the season, every day since May 27, with the best record in league (51-34).
• Four of five N.L. West teams have losing records. First-place Arizona barely has a winning record (43-41).
• The Dodgers, with an N.L. record $216 million payroll, wallowing in last place for eight weeks until Tuesday. On July 4 they were tied for second, only 2 ½ games from first.
• The Nationals, a pre-season favorite, struggling to stay above .500.
• The Tigers, a pre-season favorite to win perhaps everything, struggling to hold onto A.L. Central lead.
• The Marlins and the Astros compete for recognition as the majors’ worst team.
• Yasiel Puig, a Cuban dynamo, tears up the N.L. in his first month in the majors, raising legitimate questions about Dodgers’ delayed call-up while they languished in last.
• Miguel Cabrera of Detroit threatens to win his second successive Triple Crown, leading the A.L. in batting average (.364) and runs batted in (85) but Chris Davis of Baltimore looms large in his way, ahead of him in home runs (32-26) and second in hitting (.331) and r.b.i. (83).
• The Tigers’ Max Scherzer, the first pitcher to mount a 13-0 record since Roger Clemens in 1986, leads an impressive array of pitchers, including Patrick Corbin of Arizona (9-1), the Rays’ Matt Moore (11-3), the Mets’ Matt Harvey (7-2), Jordan Zimmerman of the Nationals (12-3), Boston’s Clay Buccholz, the Cardinals’ Adam Wainwright (11-5) and Lance Lynn (all 10-3) and the Pirates’ Gerrit Cole, winner of all four of his starts after his delayed call-up.

For as long as I remember July 4 was cited as a telltale date on the baseball calendar. Teams in first place that day, the theory went, would be in first place at the end of the season.

I don’t recall if the statistics supported the theory, and they aren’t available now, as far as I could determine. In addition the MLB format has changed. Beginning in 1969, the two leagues each were divided into two divisions, creating four first places instead of two.

Elias Sports Bureau has provided first-place figures since 1969.

Since 1969 (excluding the strike-interrupted seasons of 1981 and 1994), teams that woke up in first place July 4 finished the season in first place 127 times and did not end the season in first 88 times. Thus the theory worked 57.7 percent of the time.

Reducing the sample to a more recent period, beginning in 1995, the start of the wild-card era, teams leading their divisions the morning of July 4, including teams tied for first, finished the season in first 67 times and failed to finish first 47 times. Those results come to 58.8 percent.

The ratio is basically the same no matter what period is used. Take the last 10 years, and the percentage is 58.3 percent. Use the last 5 years, and the percentage is 56.7 percent.

With the playoffs expanded to two wild cards in each league, there is less need for teams in first on July 4 to be in first at the end of the season. But it certainly is still the safest way to go.

If the Pirates, for example, are able to maintain their position in first, they would be assured of making the playoffs for the first time since 1992. That was also the last time they had a winning season record.

But at this time last year they were in first place with a winning record, and they were unable to maintain either. It’s actually pretty remarkable, considering their two-decade history, that the Pirates have been in first place in the N.L. Central the last two July 4ths.

A year ago the Pirates were tied with the Reds the morning of July 4. That night they were a game ahead. They remained in first or tied for first for another week. They improved their record from 8 games over .500 July 3 to 16 over (63-47) Aug. 8, but someone pulled the plug and they spiraled out of control, losing 36 of their last 52 games and finishing in fourth place four games under .500.

On this July 4 they were two games ahead of the Cardinals in the morning, 21 games over .500 with the best records in the majors.

They could lose 50 of their last 79 games and still finish .500, but they seem to have bigger things in mind. There is still plenty of time for the Pirates to stage another collapse, but I think Frank Coonelly, the president, and Neal Huntington, the general manager, might have finally got it right.

I was skeptical when they assumed command of the Pirates at the end of the 2007 season, especially because neither had front-office experience and because they hired a minor league manager with no major league experience, John Russell, to manage the team.

But they corrected that mistake with Clint Hurdle, who in his third year with the Pirates should be manager of the year, assuming he and they can avoid another collapse.