When more than 160 playwrights and producers, most of them female, filed into a Midtown Manhattan theater Monday night, they expected to hear some concrete evidence that women who are authors have a tougher time getting their work staged than men.

And they did. But they also heard that women who are artistic directors and literary managers are the ones to blame.

That conclusion was just one surprising piece of a yearlong research project that both confirms and upends assumptions about bias in the playwriting business.

“There is discrimination against female playwrights in the theater community,” said Emily Glassberg Sands, who conducted the research. Still, she said, that isn’t the whole story; there is also a shortage of good scripts by women.

Ms. Sands, a Princeton economics student who is heading to Harvard this fall for graduate work, undertook the study, but eminent economists vouched for its high quality, including Christina H. Paxson, the chairwoman of Princeton’s economics department and the newly named dean of Princeton’s Woodrow Wilson School of Public and International Affairs; Cecilia Rouse, a member of the White House Council of Economic Advisers; and Steven D. Levitt, the co-author of “Freakonomics.”

The detailed examination was done at the urging of the playwright Julia Jordan, who has been speaking out about the huge disparity between the number of shows by men that are produced and the number by women. (Ms. Jordan was a childhood friend of Mr. Levitt.)

To sort out the findings, it helps to look at the research. Ms. Sands conducted three separate studies. The first considered the playwrights themselves. Artistic directors of theater companies have maintained that no discrimination exists, rather that good scripts by women are in short supply. That claim elicited snorts and laughter from the audience when it was repeated Monday night, but Ms. Sands declared, “They’re right.”

In reviewing information on 20,000 playwrights in the Dramatists Guild and Doollee.com, an online database of playwrights, she found that there were twice as many male playwrights as female ones, and that the men tended to be more prolific, turning out more plays.

What’s more, Ms. Sands found, over all, the work of men and women is produced at the same rate. The artistic directors have a point: they do get many more scripts from men.

For the second study, Ms. Sands sent identical scripts to artistic directors and literary managers around the country. The only difference was that half named a man as the writer (for example, Michael Walker), while half named a woman (i.e., Mary Walker). It turned out that Mary’s scripts received significantly worse ratings in terms of quality, economic prospects and audience response than Michael’s. The biggest surprise? “These results are driven exclusively by the responses of female artistic directors and literary managers,” Ms. Sands said.

Amid the gasps from the audience, an incredulous voice called out, “Say that again?”

Ms. Sands put it another way: “Men rate men and women playwrights exactly the same.”

Ms. Sands was reluctant to explain the responses in terms of discrimination, suggesting instead that artistic directors who are women perhaps possess a greater awareness of the barriers female playwrights face.

For the third piece, Ms. Sands looked specifically at Broadway, where women write fewer than one in eight shows. She modeled her research on work done in the 1960s and ’70s to determine whether discrimination existed in baseball. Those studies concluded that black players had to deliver higher performing statistics — for example, better batting averages — than white players simply to make it to the major leagues.

Ms. Sands examined the 329 new plays and musicals produced on Broadway in the past 10 years to determine whether the bar was set higher. Did scripts by women have to be better than those by men?

Of course, there are many ways to define “better,” but on Broadway, with the exception of three nonprofit theaters, everyone can agree that one overriding goal is to make a profit. So did shows written by women during that period make more money than shows written by men?

The answer is yes. Plays and musicals by women sold 16 percent more tickets a week and were 18 percent more profitable over all. In the end, women had to deliver the equivalent of higher batting averages, Ms. Sands said.

Yet even though shows written by women earned more money, producers did not keep them running any longer than less profitable shows that were written by men. To Ms. Sands, the length of the run was clear evidence that producers discriminate against women.

The findings are sure to spur debates within the theater community. Representatives from about a dozen New York theater companies, including the Public Theater and Lincoln Center Theater, attended. Many women in the industry have argued that a rise in the number of female artistic directors would lead to more productions of works written by women, but the study calls that claim into question.

Ms. Sands also found plays that feature women — which are more commonly written by women — are also less likely to be produced. Kathryn Walat, a playwright who attended, said, “Most startling was the reaction to women writing — and I think of my own work — about female protagonists and the unlikability of those characters.”

As for Ms. Jordan, she said, “I suspected it wasn’t pure discrimination, but I was surprised that women were driving it.” Whether the sex of Broadway producers is a factor is unclear, she said: “One thing I have learned is not to make those assumptions anymore.”

Professor Paxson, who helped to supervise Ms. Sands’s research, wrote in an e-mail response: “Each study uses different data and the best available research methods to investigate whether there is good evidence for gender discrimination in the playwriting business.”

Ms. Rouse said that the findings should “make even skeptics take note.”

Ms. Sands acknowledged shortcomings in her work as well as many unanswered questions. Most problematic, she said, was the use of Doollee.com as a database. Because the site depends on users, some information may be incomplete, outdated or incorrect.

Still, at the end of the evening, Ms. Sands, who seemed surprisingly comfortable on the stage for an aspiring economist, received the kind of reaction that many playwrights in the audience would wish for: prolonged applause.