That ratio is just an interesting coincidence. From page 38 of the report† (page 13 of the PDF), it's plain they are asserting a reduction in frequency from 4.8

That ratio is just an interesting coincidence. From page 38 of the report† (page 13 of the PDF), it's plain they are asserting a reduction in frequency from 4.8 times per month to 3.2 times (a delta of 1.6, not 1.5, as in the article): To illustrate the substantive size of these effects, Figure 1 shows predicted values for sexual frequency, varying the share of house- hold labor performed by men while setting all other variables to their means. As the figure shows, shifting from a household in which women perform all of the core household tasks to one where women perform none of the core household tasks is associated with a decline in sexual frequency of nearly 1.6 times per month. Given a mean sexual fre- quency in this sample of slightly over five, this is a large difference. The figure repre- sents two extreme values, but even house- holds in which men do 40 percent of core household task hours report substantially lower sexual frequency than households in which women perform all core housework. †http://www.asanet.org/journals/ASR/Feb13ASRFeature.pdf http://www.asanet.org/journals/ASR/Feb13ASRFeature.pdf