Matched Number

A matched telephone number is one that has a mailing address associated with it. Typically, it also has a name matched to it. The majority of matched telephone numbers are also listed telephone numbers, but some are unlisted. Unlisted numbers (those not listed with directory assistance or published in any local telephone book) can be matched to an address (and possibly a name) because the commercial vendors that perform the matching use databases that contain some unlisted telephone numbers with addresses and names, such as those that can be retrieved from public records in many states (e.g. vehicle registration lists, public tax bills, and other public records and databases). However, this matching process is not 100% reliable, since people often move or change their telephone numbers.

Whether or not a telephone number can be matched is predictive of the likelihood that a completed interview will be attained with that household in a telephone survey. A greater proportion of interviews are completed with numbers that are matched than are completed with unmatched numbers. A primary reason for this is that matched numbers have an address associated with them. As such, researchers can send advance mailings to these households when they are sampled for a telephone survey to alert them (“warm them up”) to the fact that an interviewer will be calling them. Advance letters with as small a cash incentive as $2 have been found to raise cooperation rates by approximately 10 percentage points in general population [Page 455]telephone surveys in the United States. Another important reason that cooperation rates in telephone surveys are higher for matched numbers is that those whose numbers are able to be matched are generally less likely to regard a telephone interviewer contacting them as an invasion of their privacy.

On average, matched telephone numbers require fewer callbacks than unmatched numbers to reach a proper final disposition. Thus, the calling rules used by a survey center to process matched numbers should differ from the rules used to process unmatched numbers. However, unless a survey center has its telephone samples screened for matched/unmatched status or receives this information for each number in the sample from its sample vendor, it will not be possible for the survey center to take the matched/unmatched status into account as their computer-assisted telephone interview (CATI) system processes the callback attempts.