I’ve always been a fan fo JKC Fdn, but surprised that they would actually publish this.
In the 3rd Par of the first page they clearly note that they have ZERO info on the income/other demographics of the transferring population. (Too bad, bcos that was my first question when I saw the headline of this thread, i.e., what is the income and work levels of those transferring to highly selective schools? Note, that the tippy tops like Stanford prefer non-trads transfers, while other highly selective schools like NYU have crappy finaid.) But then the report goes on to say, even given the limits, we went ahead and published this report bcos "we do believe that high-achieving students who aren’t affluent should have access to the same opportunities and resources as their more advantaged peers. "
In other words, ‘we have no idea of the economic of the transfers in this so-called study, but we’ll just assume that they are all poor’ so we can support our pov.
Yes, on average, community college students are poorer than those students who attend a highly selective college (half of which are full pay). But for JFK to make these conclusions, they NEED the economic data on the transferring students. Or, if a school like USC is in the mix, what about football transfers? 
Disappointingly poor research, IMO. The good news for them, however, is that the masses won’t see or care about the nuances.