Ec 10a was Harvard's highest-enrolled course this semester, narrowly beating out the rising CS50.

In fall 2009, computer science lecturer David J. Malan welcomed 337 aspiring coders to his introductory computer science course CS50. Four years later, the course’s enrollment has more than doubled, closing in on—but just failing to surpass—the introductory economics course Ec 10a as Harvard’s most popular class.

CS50 enrolled 759 students this term, according to preliminary course enrollment numbers posted on the Faculty of Arts and Sciences Registrar’s website. Course enrollment numbers referenced in this story are updated as of early Thursday morning.

“We're thrilled that so many students have been taking an interest in computer science,” Malan wrote in an email Wednesday night.

While Malan did not venture to speculate why so many students opted to take the course, he wrote that he and his teaching staff have “endeavored to build within CS50 a support structure atop which any student can succeed, irrespective of background.”

In another story of dramatic growth, statistics professor Joseph K. Blitzstein’s Statistics 110: “Introduction to Probability,” experienced a 56 percent increase in enrollment from last year, growing from 308 to 482.

Ec 10a, formerly known as Ec 10 prior to a listing change, remained Harvard’s most popular fall course for the third year running.

The General Education course Ethical Reasoning 18: “Classical Chinese Ethical and Political Theory,” rounded out the top three highest registered classes, drawing 701 enrollees, a 33 percent enrollment increase over last year.

Science of Living Systems 20: “Introduction to Psychology,” enrolled 373, making it this semester’s second-highest enrolled Gen Ed class.

Instructors of high-enrolled classes offered differing explanations for their course’s popularity.

Chinese history professor Michael J. Puett, who teaches Ethical Reasoning 18, attributed his course’s steadily increasing enrollment to “‘life-changing’” course materials and publicity via word of mouth.

The course’s head teaching fellow, Nuri Kim, had a slightly different take on the course’s popularity, pointing to Puett’s “outstanding” and “effortless” lectures and his growing reputation.

Kim also acknowledged that Michael J. Sandel’s perennially popular course, Ethical Reasoning 22: “Justice,” is not being offered this semester, meaning many students seeking an Ethical Reasoning credit may have turned to “Classical Chinese Ethical and Political Theory.”

Blitzstein, the Statistics 110 instructor, pointed to the applicability and elegance of his course material as explanations for the course’s high enrollment.

“I think there is an increasing realization, both at Harvard and internationally, that data are everywhere and statistics is needed everywhere there is data!” he wrote in an email. “I think [the increase in interest] reflects the fact that statistics is both aesthetically beautiful and intensely useful.”

SLS 20 head teaching fellow Roman Feiman attributed the course’s high enrollment to the strong teaching of psychology professor Daniel T. Gilbert, the course’s instructor this fall, as well as that of psychology professor Steven A. Pinker, who often teaches the course in the spring.

Feiman also pointed to both men’s bestselling books, media appearances, and general renown outside Harvard, as well as the appeal of the discipline of psychology, as explanations of student interest in the course.

Steady growth seemed to be the trend among many of Harvard’s perennially popular courses. But as computer science and statistics classes become increasingly popular, life sciences has experienced a slow but steady decline. Life Sciences 1a, Harvard’s introductory biology and chemistry course, has experienced a nearly 20 percent decrease in enrollment over the past three years, shrinking from 537 in 2010 to 448 this year.

—Staff writer Pooja Podugu can be reached at pooja.podugu@thecrimson.com. Follow her on Twitter @poojapodugu.