Stats on dev math and college graduation

I've been trying to find out for a while now about longitudinal studies on the graduation rates of students in developmental programs in college. The National Center of Education Statistics (NCES) has published a study which provides the data on that issue as well as many others. In fact you can create your own tables with their Quickstats feature. The study I looked at was the following.

Beginning Postsecondary Students Longitudinal Study (BPS), which follows first-time students beginning their postsecondary education, typically over a period of 6 years. The 1995-96 cohort was followed through 2001.

The data only talks about any remedial course, not math specifically. Nevertheless, one can see from the table that 65% of students who took any developmental course in 1995-1996 did not obtain any degree by 2001. Out of students not taking any developmental courses, 45% did not obtain any degree in that same time period.
So I do wonder if developmental courses in college are helpful only to some limited extent.