Midsize Law Firms Made 29.5% of New Partners on 23.4% of Hires

Do midsize law firms promote more partners than their weight in the hiring market would suggest? Sartori & Partners data show they do. Firms of 400-999 lawyers made 871 of the 2,955 lawyers promoted to partner between June 2025 and May 2026, or 29.5%. The same class took 23.4% of lateral arrivals between November 2025 and October 2026. For a firm choosing whether to grow its next partner at home or hire one from a rival, its size class is a fair guide to what its peers do.

This report sets two shares side by side for each of the four size classes: the share of new partners a class made, and the share of lateral arrivals it took. The windows differ. Promotion figures stop at May 2026, the last complete month, while lateral figures run to October 2026 and count every level, from associate to partner. Read the comparison as a direction, not as an exact gap.

Firms of 400-999 lawyers made 29.5% of new partners in the promotion year to May 2026. Their share of promotions runs well ahead of their 23.4% share of lateral arrivals, and no other class shows a gap that wide in the same direction. Firms of 150-399 lawyers lean the same way, more mildly: 14.9% of new partners against 13.3% of lateral arrivals. Together the two middle classes made 1,310 partners from their own ranks.

Another way to read the same figures is a rough ratio of buying to making. The 400-999 lawyers class took 3.6 lateral arrivals, at every level, for each lawyer it promoted to partner, the lowest ratio of the four classes. Firms of 1,000+ lawyers took 4.9 and firms of 150-399 lawyers 4.1. The windows are offset by five months, so the ratio ranks the classes; it does not measure them.

For a midsize firm, the home-grown partner is the norm among peers, not a fallback. A lateral partner search at a firm of 400-999 lawyers competes with an internal candidate who is probably already known to the partnership, and the newcomer will be judged against that candidate's record. Build that comparison into the business case before the search starts.

Firms of 1,000+ lawyers made 1,474 partners from their own ranks, 49.9% of the market total, while taking 53.6% of lateral arrivals. The gap is narrower than the midsize one and runs the other way. The largest class still makes more partners than any other in absolute terms: its tilt is toward buying, not away from making.

Across the whole market, Sartori & Partners figures count 0.79 lawyers promoted to partner for each lateral partner hired in the same 12 months, 2,955 against 3,749. Buying is the larger channel overall, and the class that takes more than half of all lateral arrivals, 53.6%, does most of it.

The class that leans hardest on hiring relative to its own promotions is the smallest. Firms under 150 lawyers made 5.5% of new partners against 9.7% of lateral arrivals, or 8.0 lateral arrivals for each promotion to partner. For these firms an outside hire is the usual way to add seniority, and a partner title made at home is the exception.

For a large firm, this makes a lateral partner search a routine tool rather than an emergency measure. It also means rivals of the same size are running the same searches for the same candidates, so timing and a clear offer count for more than reach.

Speed matters as much as volume when a firm sells its partnership to associates. In the last 5 years, firms of 150-399 lawyers made 27.1% of their new partners within 8 years of starting practice, the highest share of any class and above the market rate of 23.2%. At firms of 1,000+ lawyers the share was 21.8%, and at firms of 400-999 lawyers 22.4%. The class that makes the most partners for its hiring share does not make them faster.

The lead holds at the later mark too. Within 12 years, firms of 150-399 lawyers had promoted 78.0% of their partners, against 74.6% at firms of 1,000+ lawyers and 74.4% at firms under 150 lawyers. The figure for the 150-399 lawyers class rests on 1,575 promotions, so it reads as a pattern rather than as chance.

A firm of 150-399 lawyers recruiting senior associates out of larger firms therefore has a concrete offer: an earlier route to the title, backed by its own record. A firm of 1,000+ lawyers that hires partners from this class should expect candidates who reached the title sooner than its own cohort, and should settle how that seniority is recognized before the offer goes out.

Promotion and lateral hiring meet in the lawyers who move between classes. In the Sartori & Partners lateral database, firms of 400-999 lawyers sent 1,200 lawyers to firms of 1,000+ lawyers in 12 months and received 1,117 from them, and they took 408 from firms under 150 lawyers. A midsize firm trains lawyers that larger firms then buy, and it buys in turn from smaller ones.

The largest firms also see the most lawyers leave. Their median leaving rate is 14.8% a year, against 13.2% at firms of 400-999 lawyers and 11.9% at firms of 150-399 lawyers, measured on firm websites since April 2026. A class that sheds more lawyers each year has fewer senior associates reaching the partnership vote, and more seats to fill from outside.

For a midsize firm, the lawyers most likely to get a call from a larger firm are the same people its promotion pipeline depends on. A promotion decision deferred by a year can turn into a lateral departure, which the firm then has to replace by hiring.

The lateral side of the comparison is stable. Over the last 3 years, firms of 1,000+ lawyers took 52.5% of lateral arrivals and firms of 400-999 lawyers 25.0%, close to their 12-month shares of 53.6% and 23.4%. What changed is the volume of buying: lateral partner hires across the market rose 8.4% year on year, from 3,558 to 3,858 in the settled 12-month windows.

More partners are bought each year, but the share each size class takes has barely moved. The make-or-buy split by size is a structure a firm can plan around, not a one-year swing to wait out.

If you lead a firm of 1,000+ lawyers, treat lateral partner hiring as a standing program with its own budget and calendar, since your class takes 53.6% of all lateral arrivals. Pair it with retention work for senior associates: at a median leaving rate of 14.8% a year, every year of delay in promotion decisions adds seats you will later buy.

If you lead a firm of 400-999 lawyers, your promotion record is a recruiting asset. Your class made 29.5% of new partners; show associates that record in numbers and protect the cohort one to two years before the partnership vote, the group larger firms target.

If you lead a firm of 150-399 lawyers, sell speed. 27.1% of your class's partners made it within 8 years, the earliest track in the market, and that is the argument that moves a senior associate out of a larger firm.

If you lead a firm under 150 lawyers, expect to add seniority mainly by hiring: your class made 164 partners in a year. Sartori & Partners figures come from public law-firm announcements, firm websites and professional profiles, checked monthly; set your own promotion and hiring counts against them before the next partnership round.