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To Get the Right Data, Start in the Right Place: ZIP Code Accuracy

August 27, 2019

Thanks to two television series (and a third one in the works), 90210 is perhaps the most famous ZIP code. The tens of thousands of other ZIP codes toil in relative obscurity but are no less important to not just mail delivery but also a wide variety of other business functions.

Insurance companies use ZIP codes to assess risk, run marketing campaigns and send out bills. Our Subscribers use ZIP codes as part of the address when looking up a Protection Class (PC), Loss Cost (LC), or other risk data, such as earthquake hazard, for a specific structure or location.

As useful as ZIP codes are, it’s important to remember what they were originally intended to do and what can happen if you use an incorrect ZIP code in an address locator. 

A map of Seattle with a ZIP code search boxIn insurance rating, it's essential to get the street address-ZIP code pair correct.

To Get the Right Data, Start in the Right Place: Measuring Property Risk


The origin of ZIP codes — and the impact of using an incorrect ZIP code

When the U.S. Postal Service (USPS) introduced ZIP codes in 1963, its goal was to automate mail sorting.1 The codes weren’t, and still aren’t, designed for any use other than delivering mail. Using them for another purpose without understanding how they work can lead to significant problems.

For example, many people assume a ZIP code corresponds to a single city or part of one, but that’s not always the case. Two ZIP codes near our office, 98133 and 98177, both include part of Seattle and part of Shoreline. Another ZIP code farther south, 98178, includes part of Seattle and part of Tukwila.

Just as city and ZIP code boundaries don’t always align, fire district and ZIP code boundaries don’t necessarily align. As a result, entering an incorrect address-ZIP code pair into one of our products could result in an inaccurate PC and premiums that don’t reflect the property’s risk.

If you send in a batch of addresses with a request for PCs, and some have incorrect address-ZIP code pairs, your results could also be inaccurate. In either case, you won’t know the PC is inaccurate because you won’t know the address-ZIP code pair is inaccurate.

Getting data from the right source

If you aren’t sure of the correct ZIP code for an address, you probably turn to Google Maps or Bing Maps. These sources, though useful in many ways, aren’t good options for this task.

If you enter an inaccurate or even a non-existent address-ZIP code pair into Google or Bing, both will return a result that might — or might not — be accurate. Google and Bing don’t validate each address and don’t warn you about potentially inaccurate results.

In fact, we recently checked an address: 401 W ALDER RD, 99128 in both Google and Bing. Google couldn’t find the house and instead identified the center of the street. Bing went to a different town and ZIP code 11 miles away from the correct address. Neither offered a warning that the results might not be right.

In addition, ZIP codes are not static. Their boundaries sometimes change. Entire ZIP codes are occasionally retired. New development, now at extremely high levels in Washington state, sometimes necessitates new ZIP codes or accelerates boundary changes. And ZIP codes aren’t the only part of an address subject to change. Municipalities occasionally re-address individual properties or even large swaths of land. 

Our Geographic Information Systems (GIS) team knows you need more than what popular mapping apps offer. So, we leveraged our GIS expertise and our experience working with county assessors and 911 call operations to build a specialized geospatial location database that we update every month.

  • We add new addresses and update existing ones.
  • We map drive miles from a property to the nearest fire station.
  • We use data from our team of commercial property analysts and from our customers to capture new development and new fire hydrants.
  • When we learn of one new address or address change, we check with the county assessor about other new or changed addresses. In some cases, we discover hundreds or even thousands of updated locations, and we incorporate them into our monthly updates.


How WSRB Determines the Protection Class for Each Property


How to validate ZIP codes

Although the USPS never imagined the ZIP code would be used for insurance-rating purposes, it does recognize that people use ZIP codes for far more than sending mail and provides an online validation tool.

When we update our database, we use this tool because the data comes from the right source: the organization assigning and updating ZIP code-address pairs. You then get the most useful results possible from our products.

But, your results are only as accurate as the data you provide us. That’s why we include a mapping feature in Protection and Risk Search, so you can always visually check that you’re getting data for the correct location.

To ensure you get accurate risk-assessment data, you can also validate your address data with the USPS tool or use our map-based app, PropertyEDGE. Spoiler alert: PropertyEDGE is faster and gives you more than just an accurate ZIP code. 

Here’s how to use each and interpret your results.

To use the USPS tool, select the ZIP Code by Address option and enter the street address, including suite or unit number without the ZIP code. Click on Find.

USPS ZIP code locator step 1

To test out the tool, try entering the address of WSRB’s office: 2101 4TH AVE, SUITE 300, SEATTLE, WA. You’ll get the correct ZIP code and the ZIP+4 because it’s a delivery point in the USPS database. 

USPS ZIP code locator step 2The USPS lookup tool returns a result for a correct street address-ZIP code pair.

If, however, you enter an address that doesn’t exist — such as 710 1ST AVE W, SEATTLE, WA — you’ll see no ZIP+4. You may need to correct the address before using it to check a PC or LC unless it’s new construction.

USPS ZIP code locator step 3The USPS lookup tool returns a result for a non-existent address.

And, if you enter an address with an inaccurate ZIP code, the tool will correct your error.

USPS ZIP code locator step 4The USPS lookup tool corrects an inaccurate street address-ZIP code pair.

Once you’ve validated your address data, you can submit it, either on the Subscriber portion of our website or in a batch, and be confident in the accuracy of your results.

Using PropertyEDGE to validate ZIP codes

To use PropertyEDGE, simply enter an address in the search bar.

If you enter an address without a ZIP code, PropertyEDGE will return not just the correct ZIP code but also a map so you can verify the location. Here are the results for WSRB’s office, 2101 4TH AVE, SEATTLE WA. (Unlike the USPS tool, PropertyEDGE doesn’t require a suite number.)

ZIP Code lookup in PropertyEDGE step 1PropertyEDGE returns both the correct ZIP code and a map.

PropertyEDGE also provides additional information about any address you enter, information that helps you understand how valid a street address-ZIP code pair is likely to be. For example, enter 710 1ST AVE W, SEATTLE, WA 98119, and you'll see PC data for the general area along with "ADDRESS SOURCE: CENSUS." 

This means the address is not in our database of three million address points and may not be accurate. In fact, 710 1ST AVE W doesn't exist in Seattle. If your PropertyEDGE results show Census, Bing, or ZIP as the address source, check with your customer to get the correct information. 

ZIP code lookup in PropertyEDGE step 2PropertyEDGE tells you whether the street address-ZIP code pair is in our database
of three million address points.

If you enter an incorrect address-ZIP code pair, PropertyEDGE will suggest the correct address for you. Select an address to map and verify.

ZIP code lookup in PropertyEDGE step 3PropertyEDGE suggests a correct street address-ZIP code pair.

PropertyEDGE also gives you a number of other features, including all the information in Protection and Risk Search, data on multiple earthquake risk factors, and more.

If you have questions about how to use PropertyEDGE or how to get accurate results from any of our products, contact our customer service team at 206-217-0101. We are here to help you make the most of our products and work more efficiently. We also have self-serve how-to articles in our Help Center

Check out our next post on ZIP codes, where we talk about when — and when not — to use ZIP codes for risk assessment and other business analysis.

More geospatial content

[1] The Untold Story of the ZIP Code, https://www.uspsoig.gov/sites/default/files/document-library-files/2015/rarc-wp-13-006_0.pdf

Chris Jansen is WSRB’s GIS Database Administrator. He has more than 30 years of experience in GIS and cartography and has managed many data development projects to improve efficient information exchange and accurate business analysis of data.



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