When the Human Rights Campaign released its 2014 Corporate Equality Index last month, 81 Am Law 200 firms (and Magic Circle firm Clifford Chance) earned perfect scores thanks to the policies they have in place related to lesbian, gay, bisexual and transgender employees—up from the 71 that earned the distinction last year and double the number that rated so well in 2008. Another 37 firms from either the Am Law 200 or Global 100 rankings achieved scores of 90.

The gains large law firms have made on the HRC index—which rates employers on a 100-point scale and considers issues such as whether the insurance coverage companies provide employees covers same-sex partners and transgender individuals, while also rewarding employers for their public support of LGBT groups and equality laws—mirror those made across the broader corporate universe since the gay rights group first launched the workplace survey. Only 13 businesses surveyed for HRC’s first index, in 2002, earned perfect scores. This year, 304 of the 931 employers polled fell into that category. (British advocacy group Stonewall recently released its own annual ranking of the top 100 U.K. employers for LGBT staff, its list named 10 law firms, including three members of The Am Law 100: Baker & McKenzie, Hogan Lovells and Norton Rose Fulbright.)

But a decade after HRC first began to include law firms in its broader analysis of how corporate America handles LGBT issues, more than 60 Am Law 200 firms—10 from The Am Law 100; the rest from the Second Hundred—did not participate in the most recent edition of the survey and therefore did not earn a score.

According to Deena Fidas, who directs HRC’s Workplace Project and authored this year’s index, the group sent the survey to every firm on The American Lawyer’s most recent Am Law 200 list and received responses from 138 of those firms and 145 firms all told. None of the Am Law firms that failed to respond, Fidas said via email, contacted HRC to explain why. As it has in the past, she added, the group will continue to send the survey to non-responders in hopes of attracting more participants. “Part of our mission is to increase participation every year,” she said. “Some companies/firms take longer to become participants than others. The goal is to go back to non-participants every year until they take the survey and we’ve had a solid track record of success doing that.”

The most prominent member of The Am Law 100 absent from the HRC index was 2,363-lawyer Jones Day, the nation’s sixth highest-grossing firm in 2012, according to The American Lawyer’s most recent reporting on law firm financials. A Jones Day spokesman declined to comment on why the firm did not participate in the survey.

Perhaps even more noticeable among the missing: 258-lawyer Boies, Schiller & Flexner, one of whose founding partners, David Boies, famously helped lead the successful court fight that resulted in the U.S. Supreme Court overturning California’s gay marriage ban last year. Boies Schiller, it turns out, has never taken part in the HRC survey, something firm spokeswoman Dawn Schneider describes as an oversight. Schneider, who says she was unaware of the survey’s existence, adds that “the firm plans on full participation moving forward.”

Meanwhile, three of the Am Law 200 firms that did respond to the survey—Locke Lord, Ogletree, Deakins, Nash, Smoak & Stewart and Schulte Roth & Zabel—fell far short of the index’s upper tier. All three received scores of 45 and, according to HRC, lost points because their non-discrimination policies do not include protections based on gender identity and because they do not offer any transgender-inclusive health care covrage options. HRC also found the trio lacking in diversity training and LGBT inclusion efforts. Both Locke Lord and Schulte Roth were also docked for what HRC labeled a lack of engagement with the LGBT community. Ogletree got full credit on that count, but lost points for not offering medical and comprehensive health benefits to the domestic partners of LGBT employees that are comparable to what the partners and spouses of straight employees get.

Locke Lord marketing director Julie Gilbert challenges the low rating and says it is based on bad facts. She says Locke Lord’s non-discrimination policy does in fact include protections based on gender identity—a criteria worth 15 points under HRC’s rating system. She says the firm should have received at least 20 more points because contrary to what HRC found, it offers parity in spousal and partner access to such “soft” benefits as bereavement leave and relocation assistance. Beyond that, Gilbert says she, too, was unaware of the survey’s existence and can’t find any evidence that anyone at Locke Lord submitted information to HRC. “We don’t know where they got their information,” she says. “We didn’t supply it and it’s not factual.”

Liz Cooper, who co-authored the most recent index along with Fidas, said via email that HRC’s findings with regard to Locke Lord were based on the firm’s response to the survey at some point in the past and the group’s inability to turn up any contradictory information. “As a part of our rating methodology, we continue to rate employers that have submitted a survey in previous years to mitigate a self-selecting universe from year to year in the report,” Cooper said. “This is why Locke Lord continues to be rated; we rely on the information officially submitted by the firm until a new survey is submitted to update any policies and practices. I was unable to find a publicly available document or employment statement for Locke Lord noting that their non-discrimination policy includes gender identity, and was also unable to locate any details about heir domestic partner benefits offerings.”

While a Schulte Roth spokeswoman did not immediately offer a comment on the firm’s score, an Ogletree representative expressed confidence that the firm’s performance will improve in the future.

“Ogletree Deakins’ professional development and inclusion group is working jointly with stakeholders at every level of the firm—including our board of directors, executive committee, and benefits committee—to reach out to our LGBT attorneys, staff and their communities in ways that reflect the true culture of inclusion at the firm,” Michelle Wimes, Ogletree’s director of professional development and inclusion, said in a statement. “Collectively, we have implemented several key initiatives and are confident that these efforts will increase our score in the future.”