It’s the All-Star break, and the Houston Astros have 60 wins. That’s more wins than they had in all of 2013. It’s more wins than they had in all of 2012. It’s more wins than they had in all of 2011. Now, those Astros teams were supposed to be bad, and this Astros team was supposed to be good. No one ever expected it to be this good. No baseball team is ever expected to be this good.

There’s credit to be spread all around, but this is a post that’s focusing on the hitters, so, let’s focus on the hitters. I pretty much always choose to eliminate pitcher hitting performance, so, keep that minor factor in mind. The Astros, in April, had a 106 wRC+. They scored 4.5 runs per game. In May, they had a 129 wRC+. They scored 6.2 runs per game. In June, they had a 131 wRC+. They scored 5.8 runs per game. And so far in July, they have a 191 wRC+, and that’s a 191, not any other number, like 181 or 171 — it is not a typographical error. They’ve scored 9.8 runs per game. Over the past 30 days, the Astros as a team have combined for a 153 wRC+, which is incidentally right where you find Paul Goldschmidt. It’s been a month of a team of Paul Goldschmidts.

These Astros hitters have been insane. In just a short few minutes, I’d like to provide you with some historical context.

To kick off the presentation of historical context, you get to examine the present-day context. The Astros, overall, after eliminating pitchers, have a team wRC+ of 129. You know that’s good, because you know that 100 is average. How good are we talking? Here is major-league baseball as a whole:

I’m a sucker for players or teams who lead a category by a wide margin. Here, we have the Astros not just in first, but in first by 11 points, in front of the Dodgers. This is not a statistic that easily lends itself to a broad range, so we can tell the Astros are remarkable. You could also say it’s remarkable that, say, the Padres have been so bad, but the Astros are the most extraordinary team up there.

Think about that difference between first and second place. It feels like 11 points is a large spread. How does this stack up when you go throughout baseball history? I pulled team data from our leaderboards going all the way back to 1900. Here are the 10 biggest gaps between a year’s top lineup and a year’s runner-up lineup:

Best-Hitting Teams Team Season wRC+ Separation Yankees 1930 132 20 Reds 1976 130 18 Yankees 1931 133 17 Pirates 1902 126 16 Yankees 1927 135 16 Athletics 1913 127 14 Yankees 1928 126 12 Yankees 1936 122 12 Astros 2017 129 11 Giants 1924 120 11

This year’s Astros show up, and while nothing’s official yet, since the season still has another two and a half months to go, look at the years in that table. Representatives from the 20s. Representatives from the 30s. The Astros are one of two teams in there playing after the Second World War. Remember that this is supposed to be the age of parity. Within an age of parity, it should be all the more difficult to emerge as an outlier. Nevertheless, the Astros are where the Astros are.

The best-ever team wRC+, looking at non-pitchers, is 135. That mark was achieved by the 1927 Yankees. The 1931 Yankees finished at 133. If the season ended today, the 2017 Astros would rank fifth. That’s since 1900, in a sample of nearly 2,500 individual team-seasons. But the season isn’t ending today, unless something has happened in the news while I’ve been in the process of writing. How to take this into account to treat all the numbers fairly? I could, if I wanted, just look at the best-ever offensive first halves. Instead, I went to my tried and true standard deviations.

Long story short: For every major-league season since 1900, I calculated the standard deviation in team wRC+. I used that to calculate z-scores, figuring out the number of standard deviations from the mean. The mean, in this case, is always 100, which makes things simpler. Because the Astros have only played a portion of their schedule, it’s easier for them to have an extraordinary wRC+. However, this year’s league standard deviation is 10.6. Last year’s was 6.6, because there was more time given for things to settle. This is one means of adjusting for the Astros’ as-yet unfinished campaign.

No more words. A table! Here are the most outlandish good offensive teams, according to z-scores:

Best-Hitting Teams Team Season wRC+ Z-Score Reds 1976 130 2.90 Astros 2017 129 2.73 Mets 1987 116 2.56 Pirates 1902 126 2.51 Yankees 2007 120 2.51 Reds 1918 120 2.47 Blue Jays 2015 117 2.42 Athletics 1913 127 2.37 Yankees 2009 118 2.34 Yankees 1931 133 2.33

The Astros have hit 2.7 standard deviations better than average. Only one team, ever, has surpassed that over a full season — the 1976 Reds, who won 102 games and then didn’t lose a single time in the playoffs. This is only one way of looking at the best offenses, and I can’t swear it’s the best way, but this is an accurate reflection of the degree by which the Astros stand out. Most teams are fairly tightly bunched. Within that context, the Astros have done something absurd, and something that qualifies as historic, if only historic in development. We’ll see where the Astros are at the end.

They’re projected to decline. Of course they’re projected to decline. They’ve been way too unusually good, and every extreme data point is projected to regress toward a mean. By our projections, the Astros are set for a 111 team wRC+ the rest of the way, which would have them finish at 121. The biggest over-achiever has been Marwin Gonzalez. Next on the list is Jake Marisnick. Of the 12 Astros players with at least 100 plate appearances, nine of them are projected to hit worse than they have. I don’t know enough to argue that with confidence. I don’t know, for example, by how much Marwin Gonzalez has actually improved.

The bigger point is just that this is a tremendous offense, a deep offense, a potentially historic offense. I recognize that I’ve ignored baserunning, and that is a factor. It’s not really a team strong suit. Baserunning matters, but this is about the quality of the actual hitting. The Astros have hit better than any other team, and only one team has ever been so very far removed. When it comes to picking clubs to mimic, you could do a lot worse than the 1976 Reds.