Joseph – The younger they marry the lower the divorce rate. Those marrying in their low 20s have a lower divorce rate than those marrying in their upper 20s and 30s.
That’s not relevant to this point, which is about how early in their 20’s the boys get married; the reasoning not to push the boys into getting married younger than 22 (which I agree with) is that at 19-21, they’re not mature enough. Also, if this statistic is true, it’s also not clear which is the cause and which is the effect – maybe those with some relationship issues take longer to get married and are more likely to get divorced.
This is true across the frum spectrum. And in the Chasidic world where they marry as young as 18 and 19, they have a notably lower divorce rate than in the non-Chasidic world where they marry a bit later.
I don’t know where you get the idea that the divorce rate is different in these different communities, but even if so, you have failed to demonstrate that it’s because of age; perhaps those in communities who tend to marry younger also tend to endure a bad marriage without divorcing.