The number of college students enrolled in at least one online course increased for the ninth straight year, according to the Babson Survey Research Group's annual survey of more than 2,500 colleges and universities—including both nonprofit and for-profit institutions.

The study, "Going the Distance: Online Education in the United States, 2011," reports that more than 6.1 million students took at least one online class during fall 2010—a 10.1 percent increase over the year before. An online class is defined in this survey as a course where more than 80 percent of all content is delivered online, and there are typically no face-to-face meetings with instructors.

While the growth is substantial, it is the smallest increase since fall 2006 when enrollment in online courses increased 9.7 percent. In comparison, during fall 2009, online education saw an increase of nearly a million students taking at least one online course—or 21.1 percent growth over the year before, according to the report, formerly known as the Sloan Survey of Online Learning.

The report acknowledges this dip in growth rate and speculates that the rapid increase of online enrollment may ultimately be slowing. "The slower rate of growth in the number of students taking at least one online course as compared to previous years may be the first sign that the upward rise in online enrollments is approaching a plateau," the report surmises.

Still, the growth of online education far exceeds the growth of higher education overall: Total enrollment in higher ed increased by nearly 120,000 students during fall 2010, a mere 0.6 percent increase over the year before. And, 31 percent of all students participated in an online class during the semester—up from 9.6 percent in fall 2002, when the survey was first administered.

Certain disciplines within online education saw gains and losses in enrollment between fall 2010 and fall 2011. A larger proportion of education and psychology programs saw declines in enrollment, while conversely, engineering, which had the highest proportion of declining enrollment in 2010, saw marked improvement in 2011, according to the study. Disciplines such as business and computer and information sciences have seen steady enrollment year over year, while the health professions discipline "stands alone, as it appears to be the fastest growing."

Online education has become an integral part of many colleges and universities, according to the study, with 65.5 percent of all chief academic officers reporting that "online education is critical to the long-term strategy" of an institution in 2011, up slightly from the previous year.

The reputation of the quality of online courses has also continued its upward climb—albeit only a slight increase in positive perceptions in recent years. Sixty-seven percent of academic professionals rated online education courses as the same or superior to face-to-face instruction, an increase from 57 percent in fall 2003, when this rating was first published. While this may be a positive step for proponents of online education, the study is quick to note that roughly 10 percent of the respondents have historically been detractors of online courses.

"The view that online education is 'just as good as' face-to-face instruction is by no means universally held," the study acknowledges. "While there has been a slow increase in the proportion of academic leaders that have a positive view of the relative quality of the learning outcomes for online courses as compared to comparable face-to-face courses, there remains a consistent and sizable minority that see online as inferior."