Census Enumeration Area - Dissemination Area Correspondence File

Question

A patron is working with the "Enumeration area-dissemination area correspondence files" for the 1996-2001 Census. I have just downloaded these for him from the DLI FTP server. He has sent the following request for assistance. Any help, or direction, would be appreciated.

"I can access the files, but I'm not sure they're giving me exactly what I need. I'm hoping to match specific 2001 dissemination areas within census tracts (for example dissemination area 170158 within census tract 0010.00) to a 1996 enumeration area. I can't see how to do it."

Answers

1. Since the coding of EAs is totally independent of the coding of census tracts, but _dependant_ on the coding of FEDs, the census tract that an EA falls in in a particular census is irrelevant. In other words, there is only one EA 158 in FED 17, and only one FED 17 in whatever province the user is working with in the 1996 census (Quebec, Ontario, Alberta, and British Columbia each as an FED number 17 in the 2003 RO - so the users needs to distinguish which province as well). In the 2001 census, the FED was replaced by the census division, and each CD has a unique number within the province, and each DA has a unique number withing the CD. So the province code is essential, while the census tract is irrelevant, since it is not part of the EA or the DA coding.

The province+FED code+EA code in, say 1996, with in the EA-DA correspondence file, be mapped one or more to a province+census division code+DA [+block] code(s) in the 2001 census.

If the user is mainly concerned with census tracts, maybe s/he should be using the census tract conversion tables, which were published in the census tract profile volumes until about 1996, but which we have digitized and added to the ones produced by Stats Can, and all linked at:
http://www.chass.utoronto.ca/datalib/major/georef.htm

2. If i correctly understand what your patron wishes to do, it can be done through Geosuite 1996, which is available from the DLI FTP site under the Geography/1996/Geosuite directories. Here is what I understood your patron wanting to accomplish: take a 2001 DA and find its corresponding EA or EAs in 1996. Knowing this, identify the CT in which that DA was located in 1996.

Step 1: find the corresponding 1996 EAs. Seems that you've already located the correspondence list from the 2001 Census. This
file resides under Geosuite 2001 as a text file named:ea-sd_corr.txt.

I opened this file in Wordpad (which handles the Unix end-of-line characters correctly in Windows) and did an Edit/Find for the 2001 DA provided from your patron: 59170158. There are multiple records for this DA-to-EA linkage because the correspondence is done at the Block Face level. The first occurrence is with 1996 EA 59032301. I kept pressing F3 (Find Next) working my way down the file. The next 1996 EA corresponding with this DA is EA 59032308. Pressing F3 a couple more times reaches the end of file.

DA 59170158 in 2001 is made up of parts of EA 59032301 and 59032308 in 1996.

Step 2: To find the CT in which these two EA's belonged in 1996, start a 1996 Geosuite session.

1. From the menu, select CODE SEARCH.
2. From Level at the top left of the Code Search Window, select FED. Laine noted in her reply that EA's were encoded using PR (2-digits), FED (3-digits), EA (3-digits) in 1996.
3. In the Code text box, enter: 59032. This will display the Victoria Federal summary.
4. Click NEXT and on the subsequent window, select EA and click NEXT again.
5. Click the double-right-facing arrows (>>) to move all elements to the results box.
6. Click SET CONDITIONS and for the field EAuid EQUALS, enter: 59032301
7. Click ADD; select OR and for the field EAuid EQUALS, enter: 59032308
8. Click OK and then NEXT
9. The resulting window will contain the two EA's from 1996 with their corresponding Census geography. Scrolling to the right, you will find that the CMA for these EA's is 935 and the CT is 2417.