Is there any data available on the majors of students taking freshman calculus, including information on changes over time? In the past I think engineering students were probably a hefty majority, but I suspect that that has changed quite a bit within the last 20 years, at least here in California. Circa 1996, the University of California system started requiring its biology majors to take calculus and a new flavor of calculus-based physics (a 1-year survey with calculus as a corequisite). If the population has changed a lot, then one question that could be raised is whether the traditional structure of a one-year calculus course is appropriate for the new population.
This should have all the information you need (demographic data as well as possible interventions, etc.) The linked-to file is the summary report of a multi-year multi-institutional study to understand the way calculus is taught in colleges and universities in the US. On page 11 (and coincidentally in Table 11) you will find that the 31% folks taking calculus want to be engineers, 30% want to be in the biological/life sciences and the other (ten or so) disciplines come in at the single digits (2% are math majors, 8% are business majors, etc).
This answers the demographic question, I hope. Your general question about the traditional one year calculus structure is addressed repeatedly throughout the linked-to file but maybe not with particular majors in mind. They make the argument that the challenges Calculus-teaching in the US faces are complicated and are best answered locally (perhaps) through site-dependent methods of placement, student support, curriculum and pedagogy.