The 2008-2010 ACS 3-year Summary File is accessible from the American Community Survey home page. From the ACS home page, www.census.gov, click on the Data and Documentation tab, select the option for Summary File, as shown below:


That will take you to the ACS Summary File page. Click on 2010 ACS 1-Year Summary File to go to the ACS Summary file page:



This is the ACS Summary File-it is actually comprised of three folders that are explained the next chapter.

The Summary File is organized in three folders as shown in the above screenshot. These three directories contain the same combination of files; they are simply arranged differently to accommodate various user needs:

• 2008-2010_ACSSF_All_In_l_Giant_File(Experienced-Users Only)

The "All in 1 Giant File" directory contains a zipped file, which includes geography, estimate, and margin of error files. This zipped file is ideal to download if users want estimates and margins of error for all geographies throughout the nation at once. The file is very large and should only be used by those that can easily process a very large file. For a graphical representation of this folder and its contents, see Appendix B.1.

• 2008-2010_ACSSF_By_State_All_Tables

The "By State All Tables" directory contains zipped files for each state or state level equivalent-each of the 50 states, District of Columbia, Puerto Rico, as well as cross-state geographies such as metropolitan areas. Each zipped file contains a geography file and multiple estimate and margin of error files. Downloading from these state level folders is ideal if users want all the tables for a state level geography or cross-state geographies. For a graphical representation of this folder and its contents, see Appendix B.2.

• 2008-2010_ACSSF_By_State_By_Sequence_Table_Subset

The "By State By Sequence Table Subset" directory contains folders for each state or state level equivalent--each of the 50 states, District of Columbia, Puerto Rico, as well as cross-state geographies such as metropolitan areas. Within those folders are a geography file and zipped files containing the estimate and margin of error files, one per "sequence" (sequences are explained in Chapter 2.3). Downloading from these folders is ideal if users only want a few tables for a state level geography or cross-state geographies. For a graphical representation of this folder and its contents, see Appendix B.3.

The naming convention used for the zipped files in this directory is the following:

File Name: 20101ak0001000.zip
Example	Name	Range or Type
2010	Reference Year	ACS data year (last year of the period for multiyear periods)
1	Period Covered	1=1-year, 3=3-year, 5=5-year
ak	State Level	US or abbreviations for state, District of Columbia, and Puerto Rico
0001	Sequence Number	0001 to 9999
000	Place Holder	Iteration value for future use

As Appendix B shows, the "All in 1 Giant File" and the "By State All Tables" folders contain the same tables as the "By State By Sequence Table Subset" folder. The difference is in the organization. The "By State All Tables" zipped files contain all of the sequence files for the given state, so each zipped file contains 354 files. "The All in 1 Giant File" zipped file contain all sequence files for all states, which is thousands of files.

As mentioned earlier, the zipped files are divided by state or state-level equivalents. Those state-level equivalents include the District of Columbia and Puerto Rico. There is also a level called "United States," which is for summary levels that can cross state boundaries, such as the Nation, and all Regions, Divisions, Metropolitan Statistical Areas and Tribal Reservations. The United States level does not contain tables for geographies that are always entirely within a state, such as counties and places; for those tables, go to the folder or files for that state.
The following is a table that gives examples of the types of summary levels that are in the state folders and files and those that are in the United States folders and files. A complete list of all the ACS 3-year summary levels and which folder they are in can be found in Appendix F.

Each State, DC, and Puerto Rico	United States
State County County subdivision Place Congressional districts (110th Congress) Public Use Microdata Area (PUMA) School Districts Alaska Native Regional Corporation	United States Region Division Metropolitan or urban statistical areas New England City and Town Area (NECTA) American Indian/Alaska Native/Hawaiian Home Land areas Urban areas

Detailed Tables for similar subject areas are grouped together in "sequences". A sequence number is an assigned number to a grouping of ACS tables, and it may change from year to year or product to product (1-, 3-, or 5- year data sets). The rules governing how many tables can be assigned the same sequence number depend on the following:

• There are no more than 256 columns per sequence, so the data can be read into a spreadsheet.
• Tables are grouped into sequences according to subject area, but they are not in numerical order (i.e., Table B00001 is not in sequence file 0001).
• Tables with race iterations are grouped in the same sequence.

It is critical to know the sequence number associated with a Detailed Table (Table ID) for two reasons. First, one needs it in order to access the correct estimates and margins of error files for the desired table. Second, the field start position for the estimates or margins of error of a certain Detailed Table depends on its sequence number.

The Sequence Number and Table Number Lookup file-- available as an Excel spreadsheet, text file, and SAS dataset-- lists Table IDs associated with each sequence number. This spreadsheet, formerly known as "merge_5_6&quot, is available at http://www2.census.gov/acs2010_3yr/summaryfile/. (The file is named &quotSequence_Number_and_Table_Number_Lookup&quot with the ".xls&quot, ".txt", or ".sas7bdat" extension.)

To find the sequence number associated with the table B08406, for example, a user must open and look for that Table ID in the Sequence Number and Table Number Lookup file. Shown below is a screenshot of this file, for the 2010 1-year ACS, opened to where the "tblid" is B08406. The next column in the file, "seq", shows that this Table ID is associated with the sequence number "0003". In order to access the estimate and margin of error file for Table B08406, a user will need to download the estimate and margin of error files labeled with the sequence number "0003".

There is a geography file that comes with the estimate and margin of error files. This file begins with a "g" and is an ASCII file using either a position based format or comma delimited format. A geography file exists for each state or state level equivalent.

Geography files are named using the following convention:

File Name: g20103ak.txt
Example	Name	Range or Type
g	File Type	g=geography
2010	Reference Year	ACS data year (last year of the period for multiyear periods)
3	Period Covered	1=1-year, 3=3-year, 5=5-year
ak	State Level	US or abbreviations for state, District of Columbia, and Puerto Rico

The geography files contain geographic information for an ACS tabulated area, including the name of the area. One variable on the file, called LOGRECNO, is the logical record number and is used to link the level of geography to the estimate and margin of error files. An example of how to use LOGRECNO is discusses in Chapter 2.5.

The following table provides the layout of the geography file:

Variable Name	Description	FieldSize	StartingPosition	Geographic Summary LevelsFor 1-Year Tables
RECORD CODES
FILEID	Always equal to ACS Summary File identification	6	1	All Summary Levels
STUSAB	State Postal Abbreviation	2	7	All Summary Levels
SUMLEVEL	Summary Level	3	9	All Summary Levels
COMPONENT	Geographic Component	2	12	All Summary Levels
LOGRECNO	Logical Record Number	7	14	All Summary Levels
GEOGRAPHIC AREA CODES
US	US	1	21	10
REGION	Census Region	1	22	20
DIVISION	Census Division	1	23	30
STATECE	State (Census Code)	2	24	Reserved for future use
STATE	State (FIPS Code)	2	26	040, 050, 060, 160, 230, 312, 352, 500, 795, 950, 960, 970
COUNTY	County of current residence	3	28	050, 060
COUSUB	County Subdivision (FIPS)	5	31	60
PLACE	Place (FIPS Code)	5	36	160, 312, 352
TRACT	Census Tract	6	41	Reserved for future use
BLKGRP	Block Group	1	47	Reserved for future use
CONCIT	Consolidated City	5	48	Reserved for future use
AIANHH	American Indian Area/Alaska Native Area/ Hawaiian Home Land (Census)	4	53	250
AIANHHFP	American Indian Area/Alaska Native Area/ Hawaiian Home Land (FIPS)	5	57	Reserved for future use
AIHHTLI	American Indian Trust Land/ Hawaiian Home Land Indicator	1	62	Reserved for future use
AITSCE	American Indian Tribal Subdivision (Census)	3	63	Reserved for future use
AITS	American Indian Tribal Subdivision (FIPS)	5	66	Reserved for future use
ANRC	Alaska Native Regional Corporation (FIPS)	5	71	230
CBSA	Metropolitan and Micropolitan Statistical Area	5	76	310, 312, 314
CSA	Combined Statistical Area	3	81	330
METDIV	Metropolitan Statistical Area- Metropolitan Division	5	84	314
MACC	Metropolitan Area Central City	1	89	Reserved for future use
MEMI	Metropolitan/Micropolitan Indicator Flag	1	90	010, 020, 030, 040, 314
NECTA	New England City and Town Area	5	91	335, 350, 352
CNECTA	New England City and Town Combined Statistical Area	3	96	335
NECTADIV	New England City and Town Area Division	5	99	355
UA	Urban Area	5	104	400
BLANK		5	109	Reserved for future use
CDCURR	Current Congressional District ***	2	114	500
SLDU	State Legislative District Upper	3	116	Reserved for future use
SLDL	State Legislative District Lower	3	119	Reserved for future use
BLANK		6	122	Reserved for future use
BLANK		3	128	Reserved for future use
BLANK		5	131	Reserved for future use
SUBMCD	Subminor Civil Division (FIPS)	5	136	Reserved for future use
SDELM	State-School District (Elementary)	5	141	950
SDSEC	State-School District (Secondary)	5	146	960
SDUNI	State-School District (Unified)	5	151	970
UR	Urban/Rural	1	156	010, 020, 030, 040
PCI	Principal City Indicator	1	157	010, 020, 030, 040, 312, 352
BLANK		6	158	Reserved for future use
BLANK		5	164	Reserved for future use
PUMA5	Public Use Microdata Area - 5% File	5	169	795
BLANK		5	174	Reserved for future use
GEOID	Geographic Identifier	40	179	All Summary Levels
NAME	Area Name	200	219	All Summary Levels
BTTR	Tribal Tract	6	419	256, 258, 291, 292, 293, 294
BTBG	Tribal Block Group	1	425	258, 293, 294
BLANK		50	426	Reserved for future use

This year, we created an Excel template for the geography file named "2010_SFGeoFileTemplate.xls". The template provides users with two rows containing the variable names and their descriptions (as displayed in the above table) for each column in the geography file. It is meant to be used with the comma delimited version of the geography file. The template is available at http://www2.census.gov/acs2010_3yr/summaryfile/UserTools/ in the zipped "2010_SummaryFileTemplates" folder. Here is a screenshot of the Excel file:



Each state, the District of Columbia, Puerto Rico and the set of cross-state geographies, have one geography file associated with them regardless of how the Summary File is accessed. For example, the following screenshot shows the beginning of the state geography file for Maryland. In the screenshot, the logical record numbers corresponding with the state of Maryland, Allegany County, and Anne Arundel County are circled. The logical record number for the state of Maryland is "0000001", for Allegany County it is "0000012", and for Anne Arundel County it is "0000013".


Excess spaces in the pictured geography file have been removed for illustrative purposes.

TIGER/Line Shapefiles allow data users to directly link geographic areas to data from the American Community Survey and other surveys. The TIGER/Line Shapefiles are designed for use with geographic information system (GIS) software. Learn more about TIGER/Line Shapefiles at www.census.gov/geo/www/tiger/. The variable GEOID joins the ACS Summary File to the TIGER/Line Shapefiles. For the ACS Summary File, GEOID is located in column AW of the geography file. It is not found in the estimates or margins of error files. (As discussed in previous chapters, the variable LOGRECNO is needed to join together the parts that make up the Summary File: the geography, estimates, and margins of error files). GEOID's corresponding variable in the 2010 TIGER/Line Shapefiles is GEOID10. We will walk through an example of joining these files using Kent County, Delaware. In the ACS Summary File, the GEOID is 05000US10001. In the TIGER/Line Shapefiles, the GEOID10 is 10001. (GEOID is a concatenation of all the codes associated with a given geographic area, such as the state FIPS code, county FIPS code, etc. The exact concatenation varies by geographic area. In this example, 10=state FIPS code and 001=county FIPS code.) The ACS Summary File GEOID contains the necessary information to connect to the TIGER/Line Shapefiles, but it needs to be modified in order to exactly match up. Notice that GEOID, 05000US10001, contains the GEOID10 string, 10001. In order to create an exact match of GEOID and GEOID10, it is necessary to remove all of the characters before and including the letter "S" in the ACS Summary File. By removing these characters, the new GEOID in the ACS Summary File exactly matches the field GEOID10 in the TIGER/Line Shapefiles. The following is an example of how to modify the ACS Summary File's GEOID in Excel 2007 so it can be joined with TIGER/Line Shapefiles:

1. Open the ACS Summary File comma delimited geography file in Excel. This example uses Delaware's geography file (g20101de.csv) available at www2.census.gov/acs2010_3yr/summaryfile/ with the column headers from the geography file template copied into Delaware's geography file. Learn more about the geography file template in Chapter 2.4.
2. Insert 2 blank columns to the right of the column "GEOID." Your modified GEOID will eventually go into the second column. (Note: Columns F through AV in the diagrams following are hidden for illustrative purposes.)
3. Next, select the column "GEOID."
   
4. Select the "Data" tab from the top menu, then select "Text to Columns." to Columns Wizard" box should pop up.
   
   
5. In the "Convert Text to Columns Wizard," select "Delimited" under "Choose the file type that best describes your data:" then click "Next."
   
6. Check "Other" as the delimiter and type the letter "S" into the box. Click "Next.'
   
7. In the "Data preview" window, click on the top of both columns in "Data preview" and select "Text" under "Column data format." In "Destination," select the two blank columns that you created in Step 1. Click "Finish."
   
8. Column AY should now contain the modified GEOID that corresponds to GEOID10 in the TIGER/Line Shapefiles. The second screenshot shows the TIGER/Line Shapefile for Kent County, Delaware.
   
   
9. The ACS Summary File and the TIGER/Line Shapefile should now be ready to be joined using GIS software. Visit "Working with TIGER/Line Shapefiles" at http://www.census.gov/geo/www/tiger/wwtl/wwtl.html to learn more about how to access and use the TIGER/Line Shapefiles.