Registrant variation on common demographic variables far exceeds variation in residential universities, both within and across courses. Table 3 lists summary statistics about education, age, and gender, and Table 4 lists counts and percentages of registrants from subpopulations that illustrate the variation in registrant backgrounds.

Table 3. Demographic information for registrants and certificate earners. Percentages exclude missing data (3–5% for gender, 3–6% for education, 4–8% for age).

Table 3

Table 4. Selected subpopulation counts and percentages of nonmissing data by course and for all HarvardX and MITx.

Table 4


Figure 4 shows the percentage of registrants and certificate earners, respectively, who have completed a bachelor’s degree, a master’s degree, or a doctorate. Certified registrants generally had a higher average educational level than noncertified registrants. These percentages exclude from the denominator both missing data and completed educational levels reported as “other.” Figure 5 shows the full distribution of registrants’ completed educational levels, ranging from “none” to “doctorate.” Percentages of registrants who choose not to report their education range from 3–6% across courses.

Figure 4. Percentage of registrants who reported completion of a bachelor’s degree or higher, among all registrants (light gray) and certificate-earners (dark gray) who report their education level in each course. (Nonresponse rates from 3–6% across courses.)

Figure 4

Figure 5. Distribution of completed educational levels reported by all registrants, by course. (Nonresponse rates from 3–6% across courses.)

Figure 5

The median completed educational level across all courses was “bachelor’s” with one exception: HealthStat certificate earners had a median completed educational level of “master’s.” The two courses with the highest percentages of registrants with earned doctorates were HealthStat and Biology:7.00x, with percentages near 10%. Among those with lower levels of completed education, Table 4 and Figure 6 also show that the percentages of registrants who have, at most, a high school degree or less range from 15% (HealthStat) to 43% (MechRev:8.MReV). In many technical courses, around 5% of registrants have only completed junior high/middle school or less. This reinforces our earlier point that seemingly small percentages of registrants with low educational attainment can be a large number (over 8000 registrants without high school degrees for CS50X, over 3000 for CS-1:6.00x and CS-2:6.00x).


Figure 6 shows the age distribution in 2013 as estimated by the birth year provided at edX registration. The median age for all registrants is below 30 in every course, but the median age for certificate earners is higher than that of all registrants in all courses. The median age of certificate earners is particularly high in HeroesX, at 36. As might be expected from the course topics, as well as the relationship between age and educational attainment, the average HarvardX registrant is both older and has a higher completed educational level than the average MITx registrant. HeroesX and Biology:7.00x had particularly broad age distributions. All age distributions show considerable positive skew, in particular in HeroesX and JusticeX, with more than 10% of registrants in their 50s and above, and around a quarter of registrants who are in their 30s. Table 4 lists numbers and percentages of registrants with ages 15 and younger and ages 50 and older.

Figure 6. Distributions of the reported ages of registrants in each course as “box and whisker” plots, with the median reported age of all registrants (horizontal line) and certificate earners (diamond) shown. Box borders are the 25th and 75th percentiles. Whiskers terminate at the 5th and 95th percentiles. (Nonresponse rates from 4–8% across courses.)

Figure 6


Figure 7 shows the gender distribution across courses. On average, science, technology, engineering, and mathematics (STEM) courses have lower percentages of female registrants than courses that are not conventionally described as STEM courses (including HealthEnv, HeroesX, GlobPov:14.73x, and JusticeX). In many STEM courses, certificate earners are less likely to be female than registrants overall, although the magnitudes of distributional gender differences between certificate earners and registrants are small.

Figure 7. Percentage of registrants reporting a gender of female in each course, for all registrants and certificate earners. (Nonresponse rates from 3-5% across courses.)

Figure 7