Sluggish leasing activity in office and retail space in the first half of the year marks an end to a period of steady growth. Palm Beach County’s vacancy rate increased slightly during the second quarter to 16.2 percent, the highest since late 2004. Broward County’s rate rose to 14.3 percent. Mark Pateman, a broker with Cushman & Wakefield, says timing plays a role, as well as a bad economy. Tenants and most businesses are reluctant to make long-term decisions in an uncertain market and an election year, he said.