Documentation: ACS 2009 (1-Year Estimates)
you are here: choose a survey survey document chapter
Publisher: U.S. Census Bureau
Document: ACS 2009-1yr Summary File: Technical Documentation
citation:
Social Explorer; U.S. Census Bureau; American Community Survey 2009 Summary File: Technical Documentation.
ACS 2009-1yr Summary File: Technical Documentation
Appendix C. User Notes
Jam Values
Some data values represent unique situations where either the information to be conveyed is an explanation for the absence of data, represented by a symbol in the data display, such as "(X)", or the information to be conveyed is an open-ended distribution, such as 115 or greater, represented by 115+.

The following special data values (and their meaning), can appear in the ACS Summary File table as an explanation for the absence of data:

Missing Value = ".": A dot ".", indicates that the estimate is unavailable. All ACS tables contain these values when estimates are missing due to certain special conditions.

Filtered Value or Geographic Restriction =" ": A blank indicates that a value is filtered or is not shown due to a geographic restriction.

Margin of Error (MOE) = 0: Estimate is controlled, which indicates the estimates are controlled and a statistical test is not appropriate.

Rounding Rules, Margin of Errors (MOE), and Standard Errors (SE)
  1. B00001, B00002, B98001, and B98002 are sample counts, not estimates, and do not have margin of error (MOE) and standard error (SE) associated with them. Tables in series B99* imputation tables and B98* quality measure tables (except B98001 and B98002) do not provide margin of error calculations. The margin of error and standard error calculation are set to -1 for these tables.
  2. B. There are a few special rules on how certain margin of error and standard error are determined for ACS estimates. The accuracy of the estimate (decimal place) within the detailed tables determines how many digits the standard error is rounded. The only exceptions to these rules are tables B19082 (Shares of aggregate household income by quintile) and B19083 (GINI index of income inequality). Estimates are rounded to 2 decimal places for all estimates and the margin of error to 3 decimal places.


Display of Estimates
Display of whole numbers in the summary files: The estimates in the summary files are stored using standard notation instead of in scientific notation. The largest estimate in a Summary File contains 14 digits and stored as whole numbers.

The following list shows median and ratio tables, their table types, and accuracy.

Table ID Table Title Table Type Accuracy
B01002 MEDIAN AGE BY SEX MEDIAN Tenths
B01002A MEDIAN AGE BY SEX (WHITE ALONE) MEDIAN Tenths
B01002B MEDIAN AGE BY SEX (BLACK OR AFRICAN AMERICAN ALONE) MEDIAN Tenths
B01002C MEDIAN AGE BY SEX (AMERICAN INDIAN AND ALASKA NATIVE) MEDIAN Tenths
B01002D MEDIAN AGE BY SEX (ASIAN ALONE) MEDIAN Tenths
B01002E MEDIAN AGE BY SEX (NATIVE HAWAIIAN AND OTHER PACIFIC ISLANDER ALONE) MEDIAN Tenths
B01002F MEDIAN AGE BY SEX (SOME OTHER RACE ALONE) MEDIAN Tenths
B01002G MEDIAN AGE BY SEX (TWO OR MORE RACES) MEDIAN Tenths
B01002H MEDIAN AGE BY SEX (WHITE ALONE, NOT HISPANIC OR LATINO) MEDIAN Tenths
B01002I MEDIAN AGE BY SEX (HISPANIC OR LATINO) MEDIAN Tenths
B05004 MEDIAN AGE BY CITIZENSHIP STATUS BY SEX MEDIAN Tenths
B06002 MEDIAN AGE BY PLACE OF BIRTH IN THE UNITED STATES MEDIAN Tenths
B06002PR MEDIAN AGE BY PLACE OF BIRTH IN PUERTO RICO MEDIAN Tenths
B07002 MEDIAN AGE BY RESIDENCE 1 YEAR AGO IN THE UNITED STATES MEDIAN Tenths
B07002PR MEDIAN AGE BY RESIDENCE 1 YEAR AGO IN PUERTO RICO MEDIAN Tenths
B08103 MEDIAN AGE BY MEANS OF TRANSPORTATION TO WORK MEDIAN Tenths
B08503 MEDIAN AGE BY MEANS OF TRANSPORTATION TO WORK FOR WORKPLACE GEOGRAPHY MEDIAN Tenths
B12008 MEDIAN AGE AT FIRST MARRIAGE MEDIAN Tenths
B12008A MEDIAN AGE AT FIRST MARRIAGE (WHITE ALONE) MEDIAN Tenths
B12008B MEDIAN AGE AT FIRST MARRIAGE (BLACK OR AFRICAN AMERICAN ALONE) MEDIAN Tenths
B12008C MEDIAN AGE AT FIRST MARRIAGE (AMERICAN INDIAN AND ALASKA NATIVE ALONE) MEDIAN Tenths
B12008D MEDIAN AGE AT FIRST MARRIAGE (ASIAN ALONE) MEDIAN Tenths
B12008E MEDIAN AGE AT FIRST MARRIAGE (NATIVE HAWAIIAN AND OTHER PACIFIC ISLANDER ALONE) MEDIAN Tenths
B12008F MEDIAN AGE AT FIRST MARRIAGE (SOME OTHER RACE ALONE) MEDIAN Tenths
B12008G MEDIAN AGE AT FIRST MARRIAGE (TWO OR MORE RACES) MEDIAN Tenths
B12008H MEDIAN AGE AT FIRST MARRIAGE (WHITE ALONE, NOT HISPANIC OR LATINO) MEDIAN Tenths
B12008I MEDIAN AGE AT FIRST MARRIAGE (HISPANIC OR LATINO) MEDIAN Tenths
B19082 SHARES OF AGGREGATE HOUSEHOLD INCOME BY QUINTILE GINI Tenths
B19083 GINI INDEX OF INCOME INEQUALITY GINI Thousandths
B23013 MEDIAN AGE BY SEX FOR WORKERS 16 TO 64 YEARS MEDIAN Tenths
B23020 MEAN USUAL HOURS WORKED IN THE PAST 12 MONTHS FOR WORKERS 16 TO 64 YEARS RATIO Tenths
B23021 MEAN WEEKS WORKED IN THE PAST 12 MONTHS FOR WORKERS 16 TO 64 YEARS RATIO Tenths
B25010 AVERAGE HOUSEHOLD SIZE OF OCCUPIED HOUSING UNITS BY TENURE RATIO Hundredths
B25018 MEDIAN NUMBER OF ROOMS MEDIAN Tenths
B25021 MEDIAN NUMBER OF ROOMS BY TENURE MEDIAN Tenths
B25071 MEDIAN GROSS RENT AS A PERCENTAGE OF HOUSEHOLD INCOME IN THE PAST 12 MONTHS (DOLLARS) MEDIAN Tenths
B25092 MEDIAN SELECTED MONTHLY OWNER COSTS AS A PERCENTAGE OF HOUSEHOLD INCOME IN THE PAST 12 MONTHS MEDIAN Tenths


Data Release Filtering Rules
Data release filtering rules. Filtering rules, based on statistical reliability of the survey estimates, are used because certain geographic areas contain detailed tables include estimates whose level of reliability is unacceptable. The data release rules for the American Community Survey data tables include the following.

Every base table consists of a series of estimates. If more than half the estimates are not statistically different from 0 (at a 90 percent confidence level), then the table fails. Each estimate is subject to sampling variability that is summarized by its standard error. Dividing the standard error by the estimate yields the coefficient of variation (CV) for each of the estimates. (If the estimate is 0, a CV of 100 percent is assigned.) To implement this requirement for each table at a given geographic area, CVs are calculated for each of the table's estimates, and the median CV value is determined. If the median CV value for the table is less than or equal to 61 percent, the table passes for that geographic area; if it is greater than 61 percent, the table fails. Tables that are too sparse will fail this test. In that case, the table will not be published for that geographic area. Whenever a table fails, a simpler table that collapses some of the detailed lines together can be substituted for the original, more detailed table. The rules are then applied to the simpler table. If it passes, the simpler table is released. If it fails, none of the estimates for that particular table is released for this geographic area. These rules are applied to single-year period estimates and multi-year period estimates based on three years of sample data.