While there’s growing belief that U.S. corporate boards are too male, the question remains: How many women is enough? According to a new survey, one in 10 directors still believe that the “optimal” number is somewhere between 20% and, well, zero.

Perhaps not surprisingly, 97% of respondents who said that women should hold just a sliver of board seats are male. But it’s not just gender that’s at play here, says Paula Loop, leader of PwC’s Governance Insights Center, which conducted the study. “An important thing to remember is that the average board member age is 63—there are some generational things here.”

screen-shot-2016-10-11-at-3-03-57-pm Courtesy of PwC

PwC’s 2016 annual Corporate Directors study, released Tuesday, includes responses from 884 public company directors, 83% of whom are male and 17% of whom are female. The report looks at a range of board-related issues, including diversity and recruitment.

The survey isn’t all doom and gloom. On that same question (“What is the optimal percentage of female representation on public company boards?”), a full 43% of respondents chose 41% to 50%.

While only 41% of directors said gender diversity is very important, that’s a notable uptick from 2014, when 37% gave the same answer. Outside influences seem to be a key factor in that shift, with nearly half of directors telling PwC that they added a diverse board member over the past year in response to investor pressure. (The survey did not provide a definition of “diverse.”) “Even SEC chair Mary Jo White has been quite outspoken about disclosure [of boardroom diversity],” says Loop. “All that public pressure, investor pressure is resonating.”

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The trends in how boards look for new members are also encouraging. The vast majority of candidates are still sourced from board member recommendations, but investor suggestions (18%) and public databases (11%) are slowly gaining ground. The use of sources other than current directors’ networks tends to help women, since male board members tend to know—and nominate—other men.

The survey contains one other clue about why boards have been so slow to diversify. Overall, only about a quarter of respondents said they believe there are a significant number of qualified diverse candidates. There is, however, a clear gender split on that issue, with 93% of women saying that they at least “somewhat” believe that there plenty of qualified non-male, non-white candidates out there. Until that gap is closed, it seems unlikely that the pace of progress will improve.