The Hamilton Project has found marriage rates are decreasing across the board, but far faster in lower-income groups [1]. The marriage rate of those in the lowest income percentile have dropped almost 30%, while the highest income percentile has dropped less than 10%.
Of course, these are not absolute values, but I think it's hardly a "garbage argument" that poverty results in fewer marriages. There a number of other sources that have similar conclusions.
[1]http://www.brookings.edu/blogs/jobs/posts/2012/02/03-jobs-gr...
But more importantly, the broad counterfactual that before WWII, broadly speaking, people were more married and less wealthy.
Furthermore its highly plausible that (so-called) breakdown of marriage (in the post-war) is correlated with non-wealth effects, such as the sexual revolution fostered by hormonal birth control and the spread/use of class A drugs (ie: culture, technology). So, in addition to wealth not explaining marriage rates (broadly) at the scale of long- time, in the short term it has competition as an explanatory variable in the micro-analytic sense. Thirdly, and importantly, the relationship of marriage as a utilitarian tool for <gaining> wealth is an altogether diferent layer of abstraction. It may be, for example, that people (in the jane austen era) married into wealth as a tactic of wealth-creation. Or, alternatively, people are for-going marriage (as in the "cant have it all generatinon") as a means to facilitate of wealth creation (or, even: protection). But these are wholly different effects/causes than the broad relatinships of wealth to marital status. They involve the precise staus of marriage itself. Furthermore, they may or may not have any bearing on the develepment of Children...so far, children haven't even been a consideration in the determinants of marriage (ei, access to sex, wealth acquisition, weath protection). The status of children may wholly be an emergent phenomenon (of marriage) or it may actually be linked to the quality of the principals (absent special instituyional support).
So, in the big scheme of things, waving around macro stuff is a bit hand-wavey. It's quite a bit more important to look at the micro-analytics and actually (a) assess them; and (b) apply them to the context at hand.
On that, I think I agree with the author of the linked essay.
This an interesting link, but it is a garbage argument. Marriage as a time series is just as plausibly (if not more-soe) inversely related to wealth. People were more poor and more likely to be married in the pre-war years (one example). Furthermore the rate of dissolution in marriages is also (in recent times) correlated with increases in wealth (postwar prosperity). Its far more likely that social causes (both technological and cultural) drive family structures. Wealth is perhaps a boundary constraint in some contexts. This latter would best explain recent trends that show a bifurcation (but this is more ~last decade or two).