The University of West Georgia has been tracking course completion rates in online courses versus non-online courses, since Fall 1998. Over time, the data fields have changed slightly, aggregating partially online courses with fully online courses in the early years but not in more recent years.
Across time, there appears to be no significant difference in completion rates for online versus non-online courses. During some terms, online course completion rates were higher and in other terms they were only slightly lower. 
UWG's own homegrown online course rates were disaggregated from USG eCore online course data. Before UWG took over administration of USG eCore, in FY09, completion rates were much lower. Since UWG took over USG eCore admin services, completion rates in online eCore courses have continued to climb and remain stable.