Table B-1. Standard Errors of Vacancy Rates by Area: 2007 (Range of 68 chances out of 100) 90-Percent Rental Rate Confidence Interval (+/-)\1 for Year-to-year of 2007 of year difference rate difference United States................... 9.7 (z) 0.3 0.4 Inside Metropolitan Areas..... 9.8 0.1 0.4 0.4 In central cities........... 10.0 (z) 0.5 0.5 Not in central cities....... 9.6 0.3 0.5 0.6 Outside Metropolitan Areas.... 9.3 -0.7 1.2 1.2 Northeast..................... 7.0 -0.1 0.5 0.5 Midwest....................... 11.5 -0.9 0.6 0.7 South......................... 12.3 0.7 0.7 0.7 West.......................... 6.7 -0.1 0.6 0.6 For-rent as a percent of all housing units United States................... 3.0 (z) 0.1 0.1 Inside Metropolitan Areas..... 3.2 0.1 0.1 0.1 Outside Metropolitan Areas.... 2.0 -0.1 0.3 0.3 Northeast..................... 2.4 (z) 0.2 0.2 Midwest....................... 3.2 -0.2 0.2 0.2 South......................... 3.6 0.2 0.2 0.3 West.......................... 2.3 (z) 0.2 0.2 90-Percent Homeowner Rate Confidence Interval (+/-)\1 for Year-to-year of 2007 of year difference rate difference United States................... 2.7 0.4 0.1 0.1 Inside Metropolitan Areas..... 2.8 0.4 0.1 0.1 In central cities........... 3.6 0.5 0.3 0.2 Not in central cities....... 2.4 0.3 0.1 0.1 Outside Metropolitan Areas.... 2.4 0.3 0.2 0.2 Northeast..................... 2.0 0.3 0.2 0.2 Midwest....................... 2.8 0.2 0.2 0.2 South......................... 3.1 0.4 0.2 0.2 West.......................... 2.5 0.5 0.2 0.2 For-sale-only as a percent of all housing units United States................... 1.7 0.2 0.1 0.1 Inside Metropolitan Areas..... 1.7 0.2 0.1 0.1 Outside Metropolitan Areas.... 1.5 0.1 0.1 0.1 Northeast..................... 1.2 0.2 0.1 0.1 Midwest....................... 1.8 0.1 0.1 0.1 South......................... 1.9 0.2 0.1 0.1 West.......................... 1.5 0.2 0.1 0.1 \1 A 90-percent confidence interval is a measure of an estimate's reliability. The larger the confidence interval is, in relation to the size of the estimate, the less reliable the estimate. Z less than 0.05 percent.