Demand for law firms' services grew at a higher clip in the second quarter of 2018 than in any quarter during the past six years, according to a new report from Thomson Reuters that states firms also achieved notable growth in rates and productivity.

Demand for legal services, measured in hours billed, rose 1.4 percent in the second quarter, Thomson Reuters said.

As has been the case for the past few years, the country's largest and most profitable firms, the Am Law 100, experienced the greatest growth in demand, ratcheting up 3.2 percent. That compared to a 0.2 percent decline for the Second Hundred (the sixth consecutive quarter of Second Hundred demand declines) and 1.8 percent demand growth for midsized firms.

Worked billing rates—the invoices that firms send to clients—rose 3.4 percent in the second quarter, marking the fourth consecutive quarter of growth above 3 percent. Am Law 100 firms again led the way with 4.2 percent growth, compared to 2.8 percent growth for the Second Hundred and 3 percent growth for midsize firms.

The upbeat results are in sync with broader reports of a strong U.S. economy, which grew at a 4.1 percent annualized rate in the second quarter, according to the U.S. Department of Commerce. They also continue a prolonged period of volatility in the law firm economy, coming on the heels of an unexpectedly soft first quarter that saw demand drop by 1 percent. On the year, demand is up 0.4 percent, which compares to six-month demand growth in 2016 and 2017 of a mere 0.1 percent.

Productivity ticked up 0.9 percent during the second quarter to bring that metric—the number of hours billed per attorney—to basically flat for 2018. The productivity increase, a rarity in recent years, was mostly due to shrinking or stagnant head count at firms.

Leading the trend in slowing personnel count are midsize firms, which shrunk their attorney rolls by 0.1 percent in the second quarter of this year. Am Law 100 firms grew head count by 1.6 percent in the second quarter, while the Second Hundred grew their ranks by 0.4 percent.

The strength of litigation practices, a segment that has underperformed in recent years, was one surprising note in the Thomson Reuters report. Demand for litigation, which grew 2.2 percent, was higher than any other practice during the second quarter. For the year, litigation demand is up 0.6 percent, marking the first time since 2012 that demand for litigators' time has been positive at the halfway point.

The Thomson Reuters report was cautiously optimistic that 2018 will be a strong year for law firms.

“At the halfway point of 2018, the large law firm market is poised for a potentially strong second half,” the report said. “However, if the past few quarters have taught us anything, it's to expect the unexpected.”