With home foreclosures on an upswing, demand for apartment rentals should be rising in the Tampa Bay area. Not so fast. The region reported the 10th largest jump in apartment vacancies — 1.1 percent — among all metro areas in the United States, according to Marcus & Millichap. The real estate company said job losses crimp household formation and force more renters to double up. Miami, Orlando and Jacksonville also figured in the top 10 for vacancy growth. Tampa's overall apartment vacancy was 7.6 percent, 1.5 percentage points above the national average. Marcus & Millichap predicted vacancies would rise dramatically across the country in 2009.