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 no sample observations or too few sample observations . It could also indicate that the estimate was removed due to Disclosure Review Board (DRB) requirements. In the margin of error files, this value could also indicate that the margin of error is unavailable for a median estimate that has been replaced with a jam value.

• Geographic Restriction =" "

A blank indicates that a value is not shown due to a geographic restriction. For example, there are some estimates that are not computed at all for certain geographies, such as tables that are not tabulated for the block group level.

• Margin of Error (MOE) = "0"

A "0" entry in the margin of error column indicates that the estimate is controlled. A statistical test for sampling variability is not appropriate. This is similar to the "*****" symbol used in American FactFinder.

• Negative 1= "-1"

This indicates that an estimate does not contain a Margin of Error. Tables B00001, B00002, and tables starting with B98 and B99 do not have margin of error (MOE) associated with them. The MOE calculations are set to -1 for these tables.

• Medians

Below is a listing of the jam values for medians. For example, if there is an estimate of "2499" for table B10010, then it does not indicate a dollar amount. It means that the median is somewhere below 2,500 and thus isn't calculated.

Jam Value	Actual Meaning	Use for Medians
0	1 or less	Age, Duration of Marriage
9	9.0 or more	Rooms
10	10.0 or less	Gross Rent as Percentage of Income, Owner Costs as Percentage of Income
50	50.0 or more	Gross Rent as Percentage of Income, Owner Costs as Percentage of Income
99	100 or less	Rent, Gross Rent, Selected Monthly Owner Costs, Monthly Housing Costs
101	101 or more	Duration of Marriage
116	115 or more	Age
199	200 or less	Tax
1001	1,000 or more	Selected Monthly Owner Costs
1939	1939 or earlier	Year Built
1969	1969 or earlier	Year Moved In
2001	2,000 or more	Rent, Gross Rent
2005	2005 or later	Year Built, Year Moved In
2499	2,500 or less	Income, Earnings
4001	4,000 or more	Selected Monthly Owner Costs, Monthly Housing Costs
9999	10,000 or less	Value
10001	10,000 or more	Tax
200001	200,000 or more	Income
250001	250,000 or more	Income, Earnings
1000001	1,000,000 or more	Value

1. B00001, B00002, B98001, and B98002 are sample counts, not estimates, and do not have margin of error (MOE) 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 calculations are set to -1 for these tables.
2. There are a few special rules on how certain margin of error are determined for ACS estimates. The accuracy of the estimate (decimal place) within the detailed tables determines how many digits the margin of error is rounded.

The only exceptions to these rules are tables B19082 (Shares of aggregate household income by quintile) and B19083 (index of income inequality, commonly known as GINI). B19082 has estimates rounded to one decimal place and MOE rounded to two decimal places. B19083 has estimates rounded to three decimal places and MOE rounded to four decimal places.

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

There are 72 tables that differ between the United States (the 50 states and the District of Columbia) and Puerto Rico. The tables are different because the comparable tables may they contain different metadata (such as C06001 having 45 cells and C06001PR having 37 cells). To identify what tables are available for Puerto Rico only look for the "PR" suffix in the table id (e.g. C06001PR). Because of that, there are sequence files that apply only to the 50 states and the District of Columbia or only to Puerto Rico:

US/State-only Sequences - Missing PR Data	PR Only Sequences - Missing US/State Data
1 (US)	108 (PR)
2 (US)	109 (PR)
17 (US)	110 (PR)
18 (US)	111 (PR)
20 (US)	112 (PR)
21 (US)	113 (PR)
22 (US)	114 (PR)
23 (US)	115 (PR)
24 (US)	116 (PR)
106 (US)	117 (PR)

Therefore, for sequences 108-117 for areas other than Puerto Rico, the sequence files exist, but they are blank.

There are six tables with 499 cells. Due to the size restriction on the sequences (no more than 245 cells), each of the tables are broken down into three sequences. These tables are only produced at the United States national level (summary level 010), and the files for these sequences will be blank for all other summary levels. The table on the next page shows the tables that contain multiple sequences: