The economic downturn means that law firms are seeing less business in the fields of real estate, mergers and acquisitions, and private equity, and that means there will be fewer students coming to Los Angeles for plum law firm gigs this summer.

Law firms often hire law school students as summer associates, much like interns. Students lucky enough to land such a job at a top firm can earn more than $3,000 a week, or about $30,000 over their vacation. The summer associate rates are tied to first-year associate salaries of $160,000.

“The economy is always something we are thinking about,” said Steve Olson, partner in charge of associate development for L.A.-based O’Melveny & Myers LLP. “The difficulty with summer associate programs is that recruiting for them is done so far in advance, the late summer and early fall.”

O’Melveny has more than 1,000 lawyers and will host 132 summer associates firmwide, down 23 from 2007. This summer, 37 law students will be working in the Los Angeles office, down from 42 in 2007.

“There has been talk about firms paring down summer classes,” said Delia Swan, a Los Angeles-based legal recruiter. “It’s not going to be a sharp overnight decline, but given this economy, we are going to see some caution.”

Recruiting partners began interviewing students last August for this year’s slots. Industry insiders said firms first evaluated the amount of available work for upcoming summer associates.

Skadden Arps Slate Meagher & Flom LLP, a 2,000-attorney firm based in New York, is hosting 312 summer associates firmwide, down from 361 in 2007. This summer, 29 law students will be working in the firm’s Los Angeles office, down from 41 in 2007.

Manatt Phelps & Phillips LLP, which has 450 attorneys, saw a slight decline in the number of law students working at the firm this summer. Twenty law students were hired firmwide, down from 21 in 2007. The firm’s Los Angeles office will be hosting 11 summer associates, down from 14 in 2007.

“We conferred with each of our division chairs and management to set goals, and we consulted with each division to project numbers that are realistic,” said Diana Iketani, chief recruiting officer with Manatt.