Let' s say that you want to create Table B08406, "Sex of workers by means of transportation to work for workplace geography," for the state of Alaska. Which files do you need? How do you read the files?
You will need three files:
- The Sequence_Number_and_Table_Number_Lookup.xls spreadsheet
- The zip file 20095ak0003000.zip and the data file e20095ak0003000.txt
- The geography file (g20095ak.txt)
Start with the Sequence_Number_and_Table_Number_Lookup.xls spreadsheet. Under the "Tblid" column, look for the value "B08406". You will see that the "Sequence Number" is "0003." This means that the data you are looking for are in the data file "e20095ak0003000.txt". How do you know this is the right file? You know this from the name of the file: the "e" stands for estimate, 2009 is the year, 5 means that these are 5-year estimates, "ak" is the state (Alaska), and "0003" is the sequence number (which contains the data for Table B08406). See Chapter 2.5 for more information.
Then use the geography file for Alaska to determine the location within the state to which the data refer. The appropriate file is g20095ak.txt, where "g" means "geography", 2009 is the year, 5 is the period estimate (in this case, 5-year estimate), and "ak" is the state. (For each state, the geography file contains the lower-case FIPS State Code.)
When you open the data file, e20095ak0003000.txt, you will see the following comma-delimited fields on the first line:
ACSSF,2009e5,ak,000,0003,0000001,333404,266147,220739,45408,36112,...
The first six fields - from "ACSSF" to "0000001" - are identifiers:
A. The first field tells you that this is an ACS Summary File;
B. The second tells you that these data are five-year estimates for the year 2005-2009 (notice the "e" before "2009" and the "5" at the end);
C. The third tells you the state ("ak" is Alaska);
D. The fourth is an iteration number;
E. The fifth is the sequence number,
F. The last is a logical record code (LOGRECNO). The LOGRECNO identifies the geographic area within a state.
The geography file, g20095ak.txt, defines the LOGRECNO. Each LOGRECNO specifies a geographic area pertaining to the state. For example, a LOGRECNO of "0000001" means the state of Alaska; a LOGRECNO of "0000002" means just the urban areas in Alaska; a LOGRECNO of "0000003" refers to just rural areas in Alaska. Notice that each state has its own geography file. For more information, see Chapter 2.4.
The other fields in the data file, from the seventh on, are data values. Each field corresponds to the value of the "line number" variable in the data dictionary. So field number seven (the 333404 value, after the sixth comma) corresponds to line number one, which is "Total". Field number eight (the 266147 value, after the seventh comma) refers to line number two, which is "Car, Truck, or Van." Field number nine (the 220739 value) corresponds to line number three, which is "Drove alone." This continues all the way up to line number 51, at which point Table B08406 ends.
Were you to read this into a computer program using software such as SAS, you could translate the first nine fields of e20095ak0003000.txt as follows:
Table ID |
Line Number |
Sequence Number |
Table Title |
Estimates |
Margin of Error |
B08406 |
|
003 |
SEX OF WORKERS BY MEANS OF TRANSPORTATION TO WORK FOR WORKPLACE GEOGRAPHY |
|
|
B08406 |
|
003 |
Universe: Workers 16 years and over |
|
|
B08406 |
1 |
003 |
Total: |
333,471 |
+/-2,630 |
B08406 |
2 |
003 |
Car, truck, or van: |
266,201 |
+/-2,589 |
B08406 |
3 |
003 |
Drove alone |
220,762 |
+/-2,439 |
B08406 |
4 |
003 |
Carpooled: |
45,439 |
+/-1,795 |
B08406 |
5 |
003 |
In 2-person carpool |
36,121 |
+/-1,596 |
B08406 |
6 |
003 |
In 3-person carpool |
5,602 |
+/-510 |
B08406 |
7 |
003 |
In 4-or-more-person carpool |
3,705 |
+/-532 |