High unemployment is wreaking havoc on the Tampa Bay apartment rental market. Vacancies have risen to 10 percent, the highest in at least a decade. The area's average rent is $819, a 4 percent decline from a year ago. The news comes from a report by Real Data Apartment Market Research. Even amid the general gloom there were pockets of pain and plenty. The lowest vacancy rate, 6.8 percent, was in and around Carrollwood, northwest of Tampa. Vacancies exceeded 13 percent in north Pinellas County and east/central Hillsborough County. Real Data doesn't expect tenants to reappear until jobs return. The Tampa Bay area shed about 56,000 jobs the past year. The glut of vacant houses across the region has also whacked demand for apartments.