Joseph, this is a late reply, but here’s my take: not “notably” less, but quantifiably less in my estimation; and it’s difficult to truly quantify without a legitimate survey.
“Very Chasidish” communities family size may vary by location with KJ and New Square outnumbering Williamsburg & BP overall – so for them it’s likely more related to the housing crisis than the tuition crisis – so it’s actually the result of “financial” crisis. (And not that many women of that generation are really past childbearing age to determine number of kids with certainty).
Of course there are many variables at work here so cause and effect on my part is mere speculation, and it’s definitely not exactly black & white, with the more progressive and educated the fewer kids as another general trend in the secular AND FRUM world. You realize it’s true when people bring examples to disprove it, while it’s the exception that proves the rule.
And “coping” issues are not to be ignored either. Our generation has less stamina and strives for more perfection than the previous generation, which definitely takes a toll. And so the doros fall…