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Multiple Matches

Objectives

• In this section you will learn how multiple matches occur and how you can help prevent or resolve them.

Overview

In some situations, it is possible for more than one street segment to meet the criteria for matching to an address. Typically, this occurs when one or more of the relax options have been selected. For example, let's look at the following address:

123 N. Main, Los Angeles, CA 90010

In this example, the street type is missing from the street address. In order for it to be properly geocoded, we will need to use one of the relax options. In this case, we will relax street type, which will result in the match being made on the basis of everything known about the address except the type of street. The problem with this approach is that in some cases, there may be more than one street with the same name located in the same zip code. For example, Main Blvd., Main Circle, etc.

A key point is that relaxing geocoding options increases the likelihood of multiple matches. This fact leads to an interesting, yet counter-intuitive, dynamic. As more relax options are enabled, the number of records that are successfully matched increases, but so does the number of records that produce multiple matches and are, therefore, not assigned coordinates. The net result is generally a net increase in matches but a relative decline in efficiency.

Minimizing Multiple Matches

The following are some of the ways in which mulitiple matches can be minimized:

1. Always start the first geocoding pass with a strict address match. In this way, the most accurate addresses will be matched first and will not be subject to possible multiple matches in later passes.

2. As you begin to add relax options, add them incrementally one at a time, rather than all at once. For a discussion on this technique, see the Section entitled, Maximizing Match Rates.

3. Always start with the cleanest addresses possible and with accurate and complete zip codes. This may mean running the database through an address/zip code standardizing program first.

4. Upon completion of the final pass, select all of the records that were assigned the value of "OM" at the end of the match code. After the records have been selected, you can begin to geocode interactively on the selected records. For each record, select the appropriate address to which the record should have been matched.

Selection Statement: "OM" $ match_code