If you look at the study (warning: PDF) you can get quantified information. Looking at page 5 you can see that a woman in .925 city (like Philadelphia) will get married a year earlier than in a 1.075 city (like Portland). So maybe the effect isn't that big after all.

Although I would expect the results would be more dramatic if we comparing the operational sex ratios of countries rather than cities. If the sexual market is unfavorable, it's a lot easier to import a mate from another city than another country.