To access the electronic questionnaire, respondents needed to have the paper questionnaire that they received in the mail in hand. Following a link from the main census web page, they were asked to enter the 22-digit Census ID printed on the paper form’s label (thus ensuring a linkage to a specific mailing address). If the 22-digit ID was confirmed as valid, then the questionnaire appeared onscreen. No publicity was given to the Internet response option.

During the time span between the opening of the online questionnaire site and the cutoff for nonresponse follow-up workload (March 3 to April 18, 2000), 89,123 submissions of Census ID numbers were made on the web site. Of these (Whitworth, 2002:5):

• 74,197 (83.3 percent) were valid Census IDs; however, only 71,333 resulted in a questionnaire submission. The other 2,864 may have been instances in which a respondent made an error entering the ID but inadvertently entered a valid number; they could have then broken off the interview and subsequently rekeyed their ID correctly. After some reconciling for unique address identifications, questionnaire data from 66,163 of the 71,133 submissions were ultimately sent on for processing; about 1,500 online submissions are unaccounted for in the Bureau’s tallies, with “no apparent explanations for this discrepancy” (Whitworth, 2002:6).

• 14,926 (16.7 percent) attempts to enter a Census ID were failures. That this proportion matches the approximate 1-in-6 coverage of the census long-form sample is perhaps telling: “since [the Census Bureau] did not advertise the Internet response option, respondents would have also had no idea that long-form households were ineligible.” Hence, “it is quite possible that many, if not most, of the submission failures” were attempts to use the Internet to answer a long-form questionnaire.

Although the vast majority of the Internet responses (98.4 percent) were each associated with only one ID number, there were some repeats of ID numbers: specifically, 1,090 ID numbers had to account for 2,853 responses. Most of these were incidents of 2 or 3 entries per ID and involved a pure replication of the same data; most likely, this was caused by a respondent clicking on the “Submit” button multiple times waiting for the browser page to load. The extreme case was a single ID associated with 17 entries; “many of these were on different days, and many with different data” (Whitworth, 2002:8–9). After final processing, 63,053 households representing 169,257 persons were included in the census through the Internet form.

The Census Bureau evaluation of the Internet response option in 2000 (Whitworth, 2002:17) deemed it “an operational success” and argued for further research: