1) Jam Values

Some data values represent unique situations where either: a) 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 b) the information to be conveyed is an open-ended distribution, such as 115 or greater, represented by 115+.

Following are the special data values (and their meaning) for case (b), which can appear in any 2008 ACS Detailed Tables containing an open-ended distribution:

Table ID	Low Value	Jam Value Definition	High Value	Jam Value Definition
B01002	0	1-	116	115+
B01002A	0	1-	116	115+
B01002B	0	1-	116	115+
B01002C	0	1-	116	115+
B01002D	0	1-	116	115+
B01002E	0	1-	116	115+
B01002F	0	1-	116	115+
B01002G	0	1-	116	115+
B01002H	0	1-	116	115+
B01002I	0	1-	116	115+
B05004	0	1-	116	115+
B06002	0	1-	116	115+
B06002PR	0	1-	116	115+
B06011	2499	2,500-	100001	100,000+
B06011PR	2499	2,500-	100001	100,000+
B07002	0	1-	116	115+
B07002PR	0	1-	116	115+
B07011	2499	2,500-	100001	100,000+
B07011PR	2499	2,500-	100001	100,000+
B07402	0	1-	116	115+
B07402PR	0	1-	116	115+
B07411	2499	2,500-	100001	100,000+
B07411PR	2499	2,500-	100001	100,000+
B08103	0	1-	116	115+
B08121	2499	2,500-	100001	100,000+
B08503	0	1-	116	115+
B08521	2499	2,500-	100001	100,000+
B10010	2499	2,500-	200001	200,000+
B19013	2499	2,500-	200001	200,000+
B19013A	2499	2,500-	200001	200,000+
B19013B	2499	2,500-	200001	200,000+
B19013C	2499	2,500-	200001	200,000+
B19013D	2499	2,500-	200001	200,000+
B19013E	2499	2,500-	200001	200,000+
B19013F	2499	2,500-	200001	200,000+
B19013G	2499	2,500-	200001	200,000+
B19013H	2499	2,500-	200001	200,000+
B19013I	2499	2,500-	200001	200,000+
B19019	2499	2,500-	200001	200,000+
B19049	2499	2,500-	200001	200,000+
B19080	2499	2,500-	200000	200,000+
B19113	2499	2,500-	200001	200,000+
B19113A	2499	2,500-	200001	200,000+
B19113B	2499	2,500-	200001	200,000+
B19113C	2499	2,500-	200001	200,000+
B19113D	2499	2,500-	200001	200,000+
B19113E	2499	2,500-	200001	200,000+
B19113F	2499	2,500-	200001	200,000+
B19113G	2499	2,500-	200001	200,000+
B19113H	2499	2,500-	200001	200,000+
B19113I	2499	2,500-	200001	200,000+
B19119	2499	2,500-	200001	200,000+
B19121	2499	2,500-	200001	200,000+
B19125	2499	2,500-	200001	200,000+
B19126	2499	2,500-	200001	200,000+
B19202	2499	2,500-	200001	200,000+
B19202A	2499	2,500-	200001	200,000+
B19202B	2499	2,500-	200001	200,000+
B19202C	2499	2,500-	200001	200,000+
B19202D	2499	2,500-	200001	200,000+
B19202E	2499	2,500-	200001	200,000+
B19202F	2499	2,500-	200001	200,000+
B19202G	2499	2,500-	200001	200,000+
B19202H	2499	2,500-	200001	200,000+
B19202I	2499	2,500-	200001	200,000+
B19215	2499	2,500-	200001	200,000+
B19326	2499	2,500-	100001	100,000+
B20002	2499	2,500-	100001	100,000+
B20004	2499	2,500-	100001	100,000+
B20017	2499	2,500-	100001	100,000+
B20017A	2499	2,500-	100001	100,000+
B20017B	2499	2,500-	100001	100,000+
B20017C	2499	2,500-	100001	100,000+
B20017D	2499	2,500-	100001	100,000+
B20017E	2499	2,500-	100001	100,000+
B20017F	2499	2,500-	100001	100,000+
B20017G	2499	2,500-	100001	100,000+
B20017H	2499	2,500-	100001	100,000+
B20017I	2499	2,500-	100001	100,000+
B21004	2499	2,500-	100001	100,000+
B22008	2499	2,500-	200001	200,000+
B23013	0	1-	116	115+
B24011	2499	2,500-	100001	100,000+
B24012	2499	2,500-	100001	100,000+
B24021	2499	2,500-	100001	100,000+
B24022	2499	2,500-	100001	100,000+
B24031	2499	2,500-	100001	100,000+
B24032	2499	2,500-	100001	100,000+
B24041	2499	2,500-	100001	100,000+
B24042	2499	2,500-	100001	100,000+
B24081	2499	2,500-	100001	100,000+
B24082	2499	2,500-	100001	100,000+
B24091	2499	2,500-	100001	100,000+
B24092	2499	2,500-	100001	100,000+
B24121	2499	2,500-	100001	100,000+
B24122	2499	2,500-	100001	100,000+
B24123	2499	2,500-	100001	100,000+
B25018	14.1	14.0+
B25021	14.1	14.0+
B25035	1939	1939-	2005	2005
B25037	1939	1939-	2005	2005
B25039	1969	1969-	2005	2005
B25057	99	100-	3001	3,000+
B25058	99	100-	3001	3,000+
B25059	99	100-	3001	3,000+
B25064	99	100-	3001	3,000+
B25071	9.9	10.0-	90.1	90.0+
B25076	999	10,000-	1000001	1,000,000+
B25077	999	10,000-	1000001	1,000,000+
B25078	999	10,000-	1000001	1,000,000+
B25083	999	10,000-	1000001	1,000,000+
B25088	99	100-	6001	6,000+
B25088	2001	2,000+
B25092	9.9	10.0-	50.1	50.0+
B25097	999	10,000-	1000001	1,000,000+
B25099	2499	2,500-	200001	200,000+
B25103	199	200-	10001	10,000+
B25105	99	100-	6001	6,000+
B25107	999	10,000-	1000001	1,000,000+
B25109	999	10,000-	1000001	1,000,000+
B25111	99	100-	3001	3,000+
B25113	99	100-	3001	3,000+
B25119	2499	2,500-	200001	200,000+

The following are the special data values (and their meaning), which can appear in the 2008 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) or Standard Error (SE) = 0: Estimate is controlled, which indicates the estimates are controlled and a statistical test is not appropriate.

2) Rounding Rules, Margin of Errors (MOE), and Standard Errors (SE)

A. B00001, B00002, B98001, and B98002 are sample counts, not estimates, and do not have MOEs and SEs associated with them. Tables in series B99* imputation tables and B98* quality measure tables (except B98001 and B98002) do not have MOEs calculated for them. The MOE and SE are set to -1 for these tables.

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) in the base tables to determine how many digits the standard error should be rounded. The only exceptions to these rules are tables

B19082: SHARES OF AGGREGATE HOUSEHOLD INCOME BY QUINTILE and B19083: GINI INDEX OF INCOME INEQUALITY. On American FactFinder (AFF), the estimates display to 2 decimal places and the MOE to 3.

3) 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 the 2008 Summary File contains 14 digits, because since SAS was used to generate the 2008 Summary File, SAS automatically stores and displays values with more than 12 digits using scientific notation, but these values were stored in the summary files as whole numbers.

Display of decimal values in the summary files: The following median and ratio tables are displayed as decimals. The following list shows these 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

4) Special Table ID Sequence Rules
The data from the American Community Survey contains 75 detailed tables that have different table layouts for the Puerto Rico than their United States counterparts. The United States version of the tables are limited to geographic areas in the US (50 states plus the District of Columbia) while the Puerto Rico versions are limited to areas in Puerto Rico. In the summary file the Puerto Rico version of the tables are in sequence file 149 through 158. Therefore, for all geographic areas within the US sequence files 149 through 158 will be blank. In addition, sequence files 1,2,23,24, 28-32, and 147 will be blank for Puerto Rico as they contain the US version of the tables. The decision to separate the files was made because the comparable tables between the US and Puerto Rico may have a different number of cells (such as C06001 with 45 cells and C06001PR with 37 cells) which would significantly alter the metadata between the US and Puerto Rico. To identify what tables are available for Puerto Rico only look for the "PR" suffix in the table id (e.g. C06001PR).

For more information on PR only sequences that are counterparts to states-only sequences, please reference the following table.

US/State-only Sequences	PR Only Sequences
1 (US)	149 (PR)
2 (US)	150 (PR)
23 (US)	151 (PR)
24 (US)	152 (PR)
28 (US)	153 (PR)
29 (US)	154 (PR)
30 (US)	155 (PR)
31 (US)	156 (PR)
32 (US)	157 (PR)
147 (US)	158 (PR

Sequences 51 and 146 contain many geo-restricted tables. Sequences 125-133 contain 3 large median tables with 499 cells. Due to the size restriction on the sequences (no more than 245 cells), each of the tables had to be broken into 3 sequences. So for example, sequence 125 contains B24121 cells 1-167, sequence 126 contains B24121 cells 168-333; sequence 127 contains B24121 cells 334-499, etc.

5) ACS User Notes
ACS User Notes are available on:
http://www.census.gov/acs/www/UseData/usernotes.html

6) Detailed Table Geographic Restrictions
ACS 2008 base tables that were subject to geographic restrictions are located on:
http://www.census.gov/acs/www/Products/users_guide/ACS2008_Data_Product_Geographic_Restriction.xls

7) Data Release Filtering Rules
Data release filtering rules. Filtering rules, based on the statistical reliability of the survey estimates, are used because certain geographic areas contain very detailed tables might include estimates whose reliability is unacceptable. The main data release rule for the ACS tables works as follows. 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 can be 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.

For a complete list of filtered detailed tables, please reference the filter_helper_file.txt located on http://www2.census.gov/acs2008_3yr/summaryfile/

8) 2008 1-Year Detailed Tables that are not available for the 2008 3-Year data release
Selected detailed tables that were published for the 2008 1-Year data release are not available for the 2008 3-Year data release. For a complete list of these tables, please reference the following file:
http://www2.census.gov/acs2008_3yr/summaryfile/
Tables_in_1Year_NOT_in_3year.xls. For more information on changes to the detailed tables please reference the 2008 Data Product Changes page on the ACS Website on:
http://www.census.gov/acs/www/Products/2008/new_notable_dp_changes.html