Law students seeking coveted positions as summer associates at large firms had slightly fewer job openings available to them in 2013 than they did last year, according to The American Lawyer's most recent Summer Hiring Survey. Among the 116 firms who responded to the relevant questions on this year's edition of the annual poll, the average summer class size was down 3.4 percent from last year, to 34.6 associates. (All told, 118 firms responded to the survey.)

Heads of recruiting at several firms attributed the dip to what they call the unpredictability built into the summer hiring routine most large law firms rely on. That process typically requires firms to estimate their employment needs two years down the road, while vying with competitors to recruit from the same pool of top talent. Indeed, just days after saying goodbye to the 2013 summer program attendees—most of them heading into their final year of law school with a full-time job offer—law firm representatives are already visiting campuses and job fairs across the country to begin filling out next year's ranks.

"It’s pretty hard to target an exact number that you think you will need two years down the road," says Peter Kazanoff, a Simpson Thacher & Bartlett partner who chairs the firm's recruiting committee. "Directionally, when we think about class sizes, everything to us starts with who we meet."

For the summer just concluded, Simpson's class size fell 29.5 percent, from 2012's 105 associates to this year's 74. In a departure from the industry's prerecession heyday, when triple-digit class sizes were more common, only seven of the surveyed firms employed at least 100 law students this year. (The survey methodology counts both first-year and second-year students in summer associate totals. For a firm-by-firm breakdown, see the chart below.)

With a class size of 190, Skadden, Arps, Slate, Meagher & Flom employed the most summer associates of any firm that participated in the 2013 survey. Gibson, Dunn & Crutcher and Latham & Watkins tied for second place with 149 summer associates apiece, followed by Kirkland & Ellis (135) and Sullivan & Cromwell (124).

At Milbank, Tweed, Hadley & McCloy, several years of conservative hiring in the wake of the credit crisis contributed to the firm's decision to nearly double its summer class this year—to 84 from 45—says Jay Grushkin, Milbank's senior hiring partner in New York. "There's an element of playing catch-up," says Grushkin. "But the primary reason is that we were busy, so we wanted to grow the firm within reason."

Other firms that saw significant gains in class size in 2013 include Schiff Hardin, which had 25 associates this summer (a 92.3 percent jump); Freshfields Bruckhaus Deringer (20 summers; a 53.8 percent increase); and Blank Rome (21 associates; a 31.3 percent hike).

Schiff Hardin managing partner Ronald Safer says the change in class size stems from the firm's adoption of a completely revamped hiring structure two years ago following the realization that "we found we were hiring great law students who may or may not turn out to be great lawyers." Now, he says, a panel of four partners interviews each candidate to home in on experiences from the students' past that demonstrate drive, initiative, teamwork, analytical abilities, networking, and other attributes.

Some firms say they've kept their programs small by design.

Kara Reidy, director of recruiting at Patton Boggs, says that in the two decades she's worked at the Washington, D.C.–based firm, modest class sizes have been a constant. "We bring in the few good ones, train them, and get them going," Reidy says. "We don’t have armies of first-years."

That said, the economy did influence the firm's decision to employ 16 summer associates in 2013, down 30.4 percent from last year's class of 23. "This year, we thought it was a prudent idea given the market to just sort of bring in fewer summer associates," Reidy says. She added that all but one of those summers got an offer to join Patton Boggs full-time after graduating.

Patton Boggs is one of two large firms to publicly acknowledge laying off associates this year. The firm said in March that it had cut 30 attorneys from its associate and staff attorney ranks, a move that was followed in late June by Weil, Gotshal & Manges, which said it had fired 60 associates. At 101, Weil's summer associate class size this year remained roughly comparable to last year's 110.

Firms with even larger proportional dips in summer programs include DLA Piper (31 summers, 45.6 percent drop); Winston & Strawn (39 summers, 36.1 percent drop); Ogletree, Deakins, Nash, Smoak & Stewart (11 summers, 35.3 percent drop); Ropes & Gray (79 summers, 32.5 percent drop); and Wilson Sonsini Goodrich & Rosati (44 associates, 33.3 percent drop).

Ropes hiring partner Richard Batchelder Jr. said the number was within the firm's normal range, and that there are plans to hire about 100 associates for next summer. He also attributed part of the drop to the firm phasing out its hiring of first-year law students this year.

Wilson Sonsini's senior director of professional services, Chris Boyd, said through a spokeswoman that the number of summer associates hired changes according to the needs of the firm's various practice groups, and that this year's class is larger than those the firm hosted in both 2011 and 2010. Ogletree director of attorney recruiting and retention Sharon Wardrip says class size is driven by individual office needs. A DLA Piper spokesman said in a statement that "given the continued uncertainty in the world economy, as well as evolving lawyer staffing models, we decided to host a smaller group in 2013 than in past years."

Winston managing partner Thomas Fitzgerald says the program has always been the firm's primary source for hiring new talent, but that as clients continue to balk at paying for the work of junior associates, the class size has diminished slightly. "Next year it will increase a bit again," Fitzgerald says. "We don't have total control; we try to give out so many offers and see what the yield is. Sometimes it's more, sometimes it's less."