You can find it here at NRO and also at Brookings. The article is fascinating from beginning to end. Along the way, Scott clarifies a number of important misconceptions:

One way to assess the extent of mobility is to ask whether people tend to be better off than their parents were at the same age — whether they experience upward absolute mobility. Research for EMP conducted by my colleagues at the Brookings Institution Julia Isaacs, Isabel Sawhill, and Ron Haskins shows that two-thirds of 40-year-old Americans are in households with larger incomes than their parents had at the same age, even taking into account the fact that the cost of living has risen. That’s pretty impressive, but it actually understates the improvement between generations. Household size declined over these decades, so incomes now are divided up among fewer family members, leaving them better off than bigger households of the past. Another EMP study shows that when incomes are adjusted for household size, four out of five adults today are better off than their parents were at the same age.
The finding of pervasive upward absolute mobility flies in the face of liberal accounts of a stagnant middle class. These accounts generally conflate disappointing growth in men’s earnings with growth in household income, which has been impressive. Growth in women’s earnings has also been impressive, but economic pessimists have twisted these bright spots to fit a gloomy narrative. They claim that household incomes have kept pace only because wives have been forced into work to make up for the shrinking bacon their husbands bring home. That ignores the long-term trend of women’s obtaining more education in industrialized nations around the world, presumably with an intention to put it to use in the work force someday. It also ignores the evidence that married men rationally chose to reduce their work hours as their wives increased theirs (even as single men continued working the same hours), and the fact that employment grew more among the wives of better-educated men than among the wives of less-educated men.
Nevertheless, incomes have not grown as fast in recent decades as they did in the middle of the 20th century. While the vast majority of Americans end up better off than their parents, the difference is probably not as great as the improvement of their parents over their grandparents was.

The argument that people are being “forced” to embrace a two-earner way of life is often connected to the rising cost of living. But of course the components of a middle-class life that have grown most expensive are medical care and education and, in certain capacity-constrained regions, housing. Housing is related to education insofar as access to education is usually bundled with housing. Others goods and services, e.g., consumer electronics, clothes, basic foodstuffs, etc., have grown cheaper. I’d suggest that it’s not a coincidence that medical care and education and housing are all subject to an unusually high degree of intervention, whether through subsidies or public provision.

While the absolute mobility picture isn’t entirely bleak, the relative mobility picture is discouraging:

The EMP/Brookings analyses break the parent and child generations into fifths on the basis of each generation’s income distribution. If being raised in the bottom fifth were not a disadvantage and socioeconomic outcomes were random, we would expect to see 20 percent of Americans who started in the bottom fifth remain there as adults, while 20 percent would end up in each of the other fifths. Instead, about 40 percent are unable to escape the bottom fifth. This trend holds true for other measures of mobility: About 40 percent of men will end up in low-skill work if their fathers had similar jobs, and about 40 percent will end up in the bottom fifth of family wealth (as opposed to income) if that’s where their parents were.
Is 40 percent a good or a bad number? On first reflection, it may seem impressive that 60 percent of those starting out in the bottom make it out. But most of them do not make it far out. Only a third make it to the top three fifths. Whether this is a level of upward mobility with which we should be satisfied is a question usefully approached by way of the following thought experiment: If you’re reading this essay, chances are pretty good that your household income puts you in one of the top two fifths, or that you can expect to be there at age 40. (We’re talking about roughly $90,000 for an entire household.) How would you feel about your child’s having only a 17 percent chance of achieving the equivalent status as an adult? That’s how many kids with parents in the bottom fifth around 1970 made it to the top two-fifths by the early 2000s. In fact, if the last generation is any guide, your child growing up in the top two-fifths today will have a 60 percent chance of being in the top two fifths as an adult. That’s the impact of picking the right parents — increasing the chances of ending up middle- to upper-middle class by a factor of three or four.

Basically, once a family makes it to the middle or upper-middle-class, the children tend to stay there. As Scott suggests later in the article, this could reflect a bias in U.S. political economy towards the protection of incumbents that damages growth. Consider, for example, the proliferation of occupational licensing restrictions. Those born into affluent kinship networks will find it easier to essentially purchase licenses, or rather the training required of those granted licenses. High barriers to entry the accreditation of new private law schools are one example of this phenomenon, as is the requirement in many states that one has to attend an accredited law school to take the bar exam.

What is clear is that in at least one regard American mobility is exceptional: not in terms of downward mobility from the middle or from the top, and not in terms of upward mobility from the middle — rather, where we stand out is in our limited upward mobility from the bottom. And in particular, it’s American men who fare worse than their counterparts in other countries. One study compared the United States with Denmark, Norway, Sweden, Finland, and the United Kingdom. It found that in each country, whether looking at sons or at daughters, 23 to 30 percent of children whose fathers were in the bottom fifth of earnings remained in the bottom fifth themselves as adults — except in the United States, where 42 percent of sons remained there
Cross-national surveys show that Americans are more likely to believe they live in a meritocracy than are residents of other Western nations. When told in an EMP poll that Sweden and Canada have more mobility than the United States, just four in ten said it was a major problem. One explanation for this finding is that high living standards and levels of absolute mobility make relative mobility of secondary concern for Americans. Indeed, EMP polling indicates that an overwhelming 82 percent prioritize financial stability — keeping what they have — over “moving up the income ladder.” In that case, tending to the American Dream demands that policymakers work to promote absolute upward mobility.
But Americans across the ideological spectrum are unhappy with the lack of relative upward mobility out of the bottom. When given the actual percentage of people stuck in the bottom, 53 percent of Americans, and half of conservatives, deemed it a “major problem.” Living up to our values therefore requires policymakers also to focus on increasing upward relative mobility from the bottom.

All of the presidential candidates would greatly profit from reading Scott’s article.