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.

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 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. 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.