Big and medium-sized law firms are still downsizing their offices, but the trend is slowing, and a growing number of firms are leasing space outside traditional central business districts, according to the latest survey by commercial real estate services company Jones Lang LaSalle.

At the same time, firms are losing their negotiating clout as demand for commercial office space from competitors heats up and rents rise in cities across the U.S., keeping the pressure on the firms to control costs.