Frequently Asked Questions About Zip Code Data

Data Questions

Purchase Questions

Data Questions

Where does the income data come from?

The data are the most current income statistics from the US Census Bureau. At the bottom of all of zip code pages, there's a section called "About the Data" that has the full citations.

I need to know the details about the US Census Bureau’s income data.

Check out the Income in the Past 12 Months section in the Census’ Subject Definitions document here:

How do I know this data is any good?

First, check out the details about Census Bureau income data (question above).

One great feature of this Census data is that margins of error are included, so you'll know how confident you can be in the income estimates. Margins of error are + or - the estimate value. For example, Carbondale city, Illinois has a 2010 poverty percent estimate of 44.5% +/- 3.3%. That means, that the US Census Bureau is 90% confident that the poverty percent for Carbondale city, Illinois is between 41.2% and 47.8%.

You can find the margins of error in the "About the Data" section at the bottom of each zip code page, and they are included in the zip code lists.

What is a ZCTA, and how is it different from a zip code?

Since the income data on this website come from the US Census Bureau, we’re using the US Census Bureau’s ZIP Code Tabulation Areas (ZCTAs), which are generalized areal representations of United States Postal Service ZIP Code service areas.

A zip code is technically a linear postal route. Here’s a fun animation about how the Census Bureau turns linear routes into polygons:

Sometimes, there isn’t a ZCTA for a “weird” zip code. Examples of weird zip codes that we’ve run into in the past include a zip only for the IRS, a zip that is a single office building or a zip code with 0 or a small population. And sometimes there aren't enough samples in a zip/ZCTA to produce an estimate (i.e. small population).

On this website, we use the terms ZCTA, zip code or zip interchangeably, because most people who we work with don’t know what a ZCTA is and the difference between a zip code and ZCTA doesn’t impact how they need to use the data. But theoretical problems could arise with using ZCTAs if you are doing a mailing list or mass mail project. We’ve never seen a problem like this happen in over 8 years of selling this data to thousands of clients, but it’s technically possible. If you are doing a mass mail project, you may need zip code data instead of ZCTA data.

If you must have United States Postal Service ZIP Code service areas and not ZCTAs, we can purchase a license for zip shape data from a private company on your behalf. Then we can use the zip shape data to create demographic estimates for zip codes rather than ZCTAs. To get a quote from the private data vendor, we need to know how many people will be accessing the data (number of users) and how you'll be using the data (i.e. internal analysis versus external facing app). And a hopefully helpful FYI, the lowest quote we've ever received for zip code shape data from a private vendor is $1,300.

How many zips/ZCTAs are in your entire list?

For the 2015 dataset, there are 32,989 ZCTAs excluding the Puerto Rico ZCTAs. A handful of these ZCTAs do not have estimates (null) or have estimates of $0.

Why Do You Recommend using Median Income instead of Average Income?

Let’s say you had the following simplified population & income numbers.

Person 1:$30,000
Person 2:$50,000
Person 3:$1,000,000

The average income for this population is $360,000. The outlier data point ($1,000,000) skews the average up. Also, the average would be skewed down if there was a person with $0 in income.

The median income for the same population above is $50,000. The outlier data point ($1,000,000) doesn’t skew the median.

If the data are equally distributed (i.e. $30K, $40K, $50K), then the average number won’t be skewed by outliers. But if the data are unequally distributed, as in the case of income, then the median is the better statistic.

Do you have data for Puerto Rico?

Yes, we do have household income data for Puerto Rico, but it's not displayed on our website. We can do a custom data pull to provide you with this information. Our custom data pulls start at $199, and more details are here just in case we're the right resource for your project. To provide you with a quote & turnaround time, we need to know what geographies (e.g. all zip codes in Puerto Rico) you need data for and what data you need (e.g. median income, average income, population & race).

I have other questions about the zip code data on this website.

Yay! We love questions. Contact us.

Purchase Questions

When will I receive my data that I’ve ordered and paid for?

Your data will be ready in 1 business day. For example, let’s say that you’ve ordered your data on a Monday. Then you’ll get an email with your data on Tuesday – assuming neither Monday nor Tuesday are holidays. If you order your data on Friday, Saturday, or Sunday, you’ll get an email with your data on Monday – again assuming Monday isn’t a holiday.

Do you have data other than income data?

Yes. We pull demographic data from over 60 government databases as well as from a handful of private data companies. We’ve pulled data for over 5,000 clients in the past 8 years and love finding unusual data that answers your questions. You can learn more about Custom Data pulls here:

Do you have historic data?

We have the income and demographic data for zips/ZCTAs in the US from the US Census Bureau for:

  • 1980, 1990, 2000, 2011, 2012, 2013, 2014 and 2015.

We can calculate an average adjusted gross income for all zips in the US from the IRS for:

  • 1998, 2001, 2002, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 and 2014.

Usually, we charge $200 per year for historic income data pulls. Either call Kristen at 1.800.939.2130 to discuss what you need, or complete the Custom Data pull form here:

We and the US Census Bureau recommend against comparing across the Census’ American Community Survey 5 year datasets (2011, 2012, 2013, 2014 & 2015) with overlapping years. Here's why.

Overlapping Collection Years

The 2011 demographics are based on American Community Survey data that were collected in the years 2007, 2008, 2009, 2010 and 2011.

The 2015 demographics are based on the American Community Survey data that were collected in the years 2011, 2012, 2013, 2014 and 2015.

So there's 1 year of overlapping data between these 2 datasets (2011). In a perfect world, it would be better to compare 2011 data to 2016 data (which isn't out yet), because 2016 will be the first year that the 5 year datasets don't contain overlapping collection years for zip codes. Other geographies, like Census tracts, county subdivisions, or places were available in the 2010 5-year ACS, and are therefore comparable to 2015 5-year ACS estimates assuming their geographic boundaries remained the same or any changes are accounted for.

Now you know the challenges of comparing Census data between years. All of that said, folks still make these comparisons all of the time, and say "well, this is the best we can do with the data, time & budget limitations that we have for this particular project."

Do you build custom, online maps?

Yes. Check out a sample map & learn more here:

Can you provide me with a list of all zips in an MSA, DMA, school district, etc.?

Probably. Either call Kristen at 1.800.939.2130 to discuss what you need, or complete the Custom Data pull form here:

Can you provide data for geographies smaller than zip codes?

Yes, you can get data for Census tracts, block groups and blocks – all of which tend to be smaller than zip codes.

  • Census tracts generally have a population size between 1,200 and 8,000 people, with an optimum size of 4,000 people. The most current Census data are available for Census tracts. For most projects, we recommend using Census tracts, because they tend to have lower margins of error than do block groups.
  • Block groups are generally defined to contain between 600 and 3,000 people. Block groups are the smallest geographic for which the most current Census data are available.
  • Census blocks are typically bounded by streets, roads, or creeks. In cities, a census block may correspond to a city block, but in rural areas where there are fewer roads, blocks may be delineated by other features. The population of a census block varies greatly. Blocks are the smallest geographic area for which Census data are available, and are only available from the Decennial Census (e.g. Census 2010). The only data published at this level are basic demographics like population by age, race, sex and household type. Income data are not available for blocks. A full list of subjects from the most recent Census can be found at

Do you provide leads? Or can you provide me with a list of people’s names, addresses and telephone numbers who meet a certain profile?

No. We only provide data for geographies, not for individuals. For example, we’ll let you know that there are 1,234 households who make over $200,000 in a zip code but not that the Smith family who lives on 987 Main Street make over $200,000.

What file format is the data in?

Usually, we provide the data in an Excel file (.xlsx), but we can also provide it as in .csv and .txt formats if you prefer. If you'd prefer a .csv or .txt, add a note like "please provide as .csv." in the field on the order form named "Any other notes or thoughts about your data needs?" If you need .sql or a database file, please call Kristen at 1.800.939.2130 or Contact Us.

I only need data for X number of zip codes or zip codes only in Y counties in a state. Can I get a lower price?

It's actually more work for us to provide a file with data for X number of zips/ZCTAs than to provide data for all zips, because we have to delete all of the zips that you don't need data for. So no, there’s no lower price available for fewer zips.

Is this a subscription service?

For 99% of our clients, we charge by the data pull. For 1% of our clients, we set up a custom subscription. The price of each subscription depends on how much data you need and how often you need data. Call Kristen at 1.800.939.2130 if you’d like to talk about setting up a custom subscription.

Do you offer an API?

No. Whenever we’ve talked to clients about building APIs in the past, it’s always been a better deal for them to get annual data dumps rather than for us to build an API.

I want city and county data added to my zip code list. Is this possible?

While it's technically possible to add both the city AND the county, our clients have been unhappy with the results when we've done this in the past.

Here's a pretend scenario that highlights the problem.

  • If a zip is in multiple counties, then that zip will be included in your Excel file multiple times. For example, pretend zip 99999 is in County 1, County 2, County 3, & County 4. So that zip would be in the Excel file 4 times with the same median & average values.
  • If a zip is in multiple cities, then that zip will be included in your Excel file multiple times. For example, pretend zip 99999 is in City A, City B, City C and City D. So that zip would be in the Excel file 4 times with the same median & average values.
  • BUT if you choose to get data for both cities & counties and a zip is in both 4 counties and 4 cities, that same zip could be in the file up to 16 times (i.e. County 1 AND City A; County 1 AND City B; etc.).

If you still want both the city and the county added to your list, add a note like "please add both the city AND county" in the field on the order form named "Any other notes or thoughts about your data needs?" when you place your order.