From the abstract:
During the 20th century there was a secular transformation within American families from a household dominated by the father to a more egalitarian one in which the wife and the children have been empowered. This transformation coincided with two major economic and demographic changes, namely the increase in economic opportunities for women and a decline in family size. To explain the connection between these trends and the transformation in family relationships we develop a novel model of parenting styles that highlights the importance of competition within the family. The key intuition is that the rise in relative earnings of wives increased competition between spouses for the love and aﬀection of their children while the decline in family size reduced competition between children for resources from their parents. The combined eﬀect has empowered children within the household and allowed them to capture an increasing share of the household surplus over the past hundred years.
UPDATE: Here is a Wall Street Journal account of the research; How Kids Displaced Dads as Rulers of the Household, According to Economists by Janet Adamy. There is a general trope, more or less agreed upon, that in the past thirty years, we have substantially demolished the positive representation of males. That in discourse, in media, and in entertainment, males are represented as needy, capricious, occasionally violent buffoons; children in men's bodies.
I think the trope is oversold but I also suspect that the underlying argument (diminishment of men) is probably measurably true. The trope is usually laid at the feet of Feminism but the research above suggests that perhaps an additional (or perhaps, main) source might be the economics of the family unit.