Source of data. --The estimates presented in this report are based on data obtained from two surveys conducted by the Bureau of the Census. Data concerning vacancy rates and tenure of occupied housing units are from the monthly sample of the Current Population Survey (CPS). Characteristics of occupied housing units are from the Quarterly Household Survey (QHS).

The Current Population Survey sample is spread over 449 areas comprising 863 counties and independent cities with coverage in each of the 50 States and the District of Columbia. Approximately 50,000 occupied households are designated for interview each month; of this number 2,250 occupied units, on the average, are visited but interviews are not obtained because the occupants are not found at home after repeated calls or are unavailable for some other reason. In addition to the 50,000, there are also about 8,500 sample units in an average month which are visited but are found to be vacant or otherwise not to be interviewed.1 Data on vacancy rates and tenure of occupied units for the first quarter 1969 are averages over the three months, January, February, and March.

The data concerning characteristics of occupied housing units are from the Quarterly Household Survey (QHS). This sample is spread over 235 areas, comprising 484 counties and independent cities. The figures in this report are based on the average of four quarterly estimates produced from interviews conducted in April, July, and October of 1968 and January of 1969. The estimates for the four quarters are each based on a one-third sample of the QHS households. Estimates for a full QHS sample are based on interviews conducted in approximately 11,500 households. These households come from a larger sample of 16,000 occupied housing units. The smaller sample is chosen by identifying the households with annual family income less than $6,000 and interviewing a sample of one-half of these. The units with income less than $6,000 retained in the sample are given twice the weight of the other units in the sample to compensate for this subsampling. In addition to the 11,500 occupied housing units interviewed, about 1,000 occupied units are visited but interviews are not obtained because the occupants are not found at home after repeated calls or are unavailable for some other reason. There are also 2,000 units in the QHS sample visited but found to be

vacant or otherwise not to be enumerated. Data for these vacant units are not included in the figures for this report.

The estimating procedures used for the QHS involve the inflation of the weighted sample results to independent estimates of the number of owner-occupied and renter-occupied housing units by urban and rural residence based on data from the Current Population Survey (CPS). These independent estimates have a lower sampling error due to the larger sample size and because other current independent estimates of the population of the United States are employed in the CPS estimation procedure.

Reliability of the estimates.--Since the estimates are based on a sample, they may differ somewhat from figures obtained if a complete census had been taken using the same schedules, instructions, and enumerators. As in any survey work, the results are subject to errors of response and of reporting as well as being subject to sampling variability.

The standard error is primarily a measure of sampling variability, that is, of the variations that occur by chance because a sample rather than the whole of the population is surveyed. As calculated for this report, the standard error also partially measures the effect of response and enumeration errors but does not measure any systematic biases in the data. The chances are about 68 out of 100 that an estimate from the sample would differ from a complete census figure by less than the standard error. The chances are about 95 out of 100 that the difference would be less than twice the standard error.

Comparison of characteristics of the vacancies for the first quarter 1969 with previous quarters (Series H-111, Nos. 1 to 55) reveals that many of the differences are small. A small difference, particularly when it is based on a small subclass of vacant housing units, should be interpreted with care. As can be seen from table A, the sampling variability in such cases may be large relative to the difference.

Illustration of the use of table of standard errors.-Table 1 of this report shows that the rental vacancy rate for the first quarter of 1969 is estimated to be 5.0 percent. Table A shows the standard error of this estimate to be approximately 0.2 percent. The chances are 68 out of 100 that the estimate would have shown a figure differing from a complete census by less than 0.2 percent. The chances are 95 out of 100 that the estimate would have shown a figure differing from a complete census by less than 0.4 percent.

UNITED STATES

GOVERNMENT PRINTING OFFICE DIVISION OF PUBLIC DOCUMENTS WASHINGTON. D.C. 20402

OFFICIAL BUSINESS

FIRST CLASS MAIL

POSTAGE AND FEES PAID

U.S. GOVERNMENT PRINTING OFFICE

Vacancy rates in rental and homeowner housing for the second quarter 1969 showed no change from the levels reported in the first quarter of the year. In the second quarter of 1969, the vacancy rate in rental housing was 5.1 percent and the vacancy rate in homeowner housing was 0.9 percent. These results are based on information obtained in sample surveys conducted by the Bureau of the Census, United States Department of Commerce.

Vacancy rates in homeowner and rental housing in the United States as a whole moved generally downward in recent years. Between the first half of 1966 and the first quarter of 1969, the vacancy

rate in homeowner housing dropped from 1.4 percent to 0.9 percent and continued at the lower level through the current quarter. The rental vacancy rate, which registered 7.7 percent in the final quarter of 1965, declined to 4.9 percent in the fourth quarter 1968 and remained at about that level through the current quarter.

In the second quarter 1969, the homeowner vacancy rate in the standard metropolitan statistical areas (SMSA's) was approximately the same as that outside SMSA's. The rental vacancy rate, by contrast, remained at a lower level inside SMSA's than the rate outside SMSA's, principally because of the low vacancy rate in the noncentral city portion of the SMSA's.