Guidance For Data Users

Hmong girl in traditional dress We field data questions year-round, often on the same themes. Look below for guidance on confusing or commonly asked questions about Minnesota data.

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I want data by zip code. What’s available?
First, users should note that zip codes are determined by the U.S. Postal Service for the purpose of delivering mail, and are not technically geographic boundaries the way we typically see them on a map. Zip codes are used to pinpoint the mail delivery location, typically at an address or a Post Office. Alternately, the U.S. Census Bureau uses nested building blocks (such as census block groups and tracts) to form geographies, but these do not reliably line up with zip codes, which often cross county and other boundaries. An additional challenge is that while census blocks use streets as edge boundaries, postal delivery routes generally service both sides of a single street.

However, because data users often desire data by postal zip codes, some economic data are available by zip codes in the Census Bureau's County Business Patterns and Economic Census. However, data from the 2000 Census, 2010 Census, and the American Community Survey (beginning with the 2007-2011 five-year estimates) are only available in a special Census geography called Zip Code Tabulation Areas (ZCTAs, or zic-tuhs ). Census ZCTAs assign to each census block the most frequently occurring ZIP code for the addresses within the block, and in this way, approximate the true postal zip code.

How closely aligned are the ZCTA boundaries to Zip Codes?
They can differ a little or a lot. A ZCTA in a densely populated area is likely to more accurately represent the area covered by a zip code than ZCTA containing a smaller population. The best way to confirm the extent to which a ZCTA represents a zip code is to overlay zip codes and ZCTAs using mapping software.

Important notes for working with ZCTAs:
- While the Postal Service changes zip codes as needed to meet operational needs, the Census Bureau only changes ZCTA boundaries with every decennial census. This means ZCTA boundaries from 2000 were updated in 2010, and will not be updated again until after 2020.
- Not all zip codes are represented with a ZCTA - for example, zip codes containing only clustered P.O. boxes, those containing only one address, or overseas zip codes may not be represented.
Find data by zip code or ZCTA on our Data By Place page.
Learn more about ZCTAs from the U.S. Census Bureau and locate shapefiles.
I’m looking for data on Minnesota’s Somali population and other African groups. How should I begin?
There are basically three ways to examine Somali and other African populations with Census data--by examining answers to questions in the U.S. Census Bureau's American Community Survey regarding country of birth, ancestry/ethnicity, or language spoken in the home.

Ancestry
Ancestry was first measured in the 1980 decennial Census, but Somali (typically appearing as Somalian in the table) ancestry first appears in the 2005 American Community Survey data tables for Minnesota. Examining ancestry data may include people born in Africa, and people born in Minnesota (or anywhere else). This means ancestry may be best for including children in Minnesota's African communities who were born in the U.S. However, because ancestry data result from an open-ended question, one challenge with ancestry data is that some people answer with a broader ancestry group. It's likely that some people of Somali or Liberian ancestry answer simply with "African" which would exclude them from ACS estimates of Somali or Liberian ancestry. Data are available by the first ancestry they selected, or total ancestry, where individuals are represented in all ancestry groups they have selected. However, users should note that in total ancestry tables, the sum of all the ancestry groups will far exceed the total population because individuals are represented multiple times.

These African ancestries are available in the tables from the 1990 and 2000 decennial Census long-form (SF3) data:
- African
- Cape Verdean
- Ethiopian
- Ghanian
- Nigerian
- Subsaharan African
- South African
Ancestry does not appear in the 2010 decennial Census data.

These African ancestries are available in the ongoing American Community Survey data:
- Kenyan
- Liberian
- Senegalese
- Sierra Leonean
- Somalian
- Sudanese
- Ugandan
- Zimbabwean
- Other Subsaharan African
Birthplace
Birthplace data are useful for seeing those in African communities and other newer populations who are foreign-born. Respondents are asked for a specific country of birth, so the challenges with differing interpretations of ancestry detailed above are avoided. Foreign-born data will not include children of immigrants who were born here, or subsequent generations born in the U.S. Currently, a large proportion of Minnesota's African communities are foreign-born, but this will change as these communities grow with more and more children born in the U.S. Data users should also be cautious of identifying a group solely by birthplace in the case of many refugee groups. For example, many Hmong now living in Minnesota were not born in Laos, but in refugee camps in Thailand.

Language
The Census Bureau collects data on language spoken at home, which is an alternative method of identifying different communities. Unfortunately, language data on African populations in the U.S. are published as an "African language." Look to ancestry or foreign-born data if you're looking for a specific country or nationality within Africa.

Find data about African groups on our Data By Topic: Immigration & Language page.
How can I learn more about Minnesota’s Hmong population using Census data?

You can obtain data on Minnesota's Hmong population from the decennial census in 2000 and 2010, and from the American Community Survey beginning in 2005. Hmong is classified as a unique race (also a subgroup of Asian) in Census data, which sometimes means you'll sometime have access to two groups. Choose the one which makes the most sense for your purposes.

"Hmong alone" - people who self-reported that Hmong is their only race
"Hmong alone or in combination" - the Hmong alone group along with those who responded that their race is Hmong in combination with another race or multiple races

Find data about Hmong and other groups on our Data By Topic: Immigration & Language page.
How are race and ethnicity defined by the U.S. Census Bureau?
Race and ethnicity are self-reported in the decennial census and the American Community Survey. Individuals may choose as many of the broad racial groups below as they wish to describe themselves, and also choose whether or not they identify as Hispanic/Latino.
The federal Office and Management and Budget requires the U.S. Census Bureau to measure five minimum racial categories:
- White - A person having origins in any of the original peoples of Europe, the Middle East, or North Africa.
- Black or African American - A person having origins in any of the Black racial groups of Africa.
- Asian - A person having origins in any of the original peoples of the Far East, Southeast Asia, or the Indian subcontinent including, for example, Cambodia, China, India, Japan, Korea, Malaysia, Pakistan, the Philippine Islands, Thailand, and Vietnam.
- American Indian or Alaskan Native- A person having origins in any of the original peoples of North and South America (including Central America) and who maintains tribal affiliation or community attachment.
- Native Hawaiian or Pacific Islander - A person having origins in any of the original peoples of Hawaii, Guam, Samoa, or other Pacific Islands.
The Census Bureau also reports two additional racial groups:
- Some other race (2010 Census only)
- Two or more races (2000 and 2010 Census)
The sum of all racial groups will equal the total population.

Hispanic/Latino ethnicity
In the current U.S. Census Bureau definition, identifying as Hispanic/Latino is an ethnicity (a concept separate from race), which means the Hispanic group may be also represented by any race or combination of races.
Can you help me understand margins of error?

When conducting surveys like the American Community Survey, the U.S. Census Bureau samples a smaller number of people that they use to represent the total population, and produces estimates from those responses. With every survey estimate, there is a corresponding margin of error that attempts to measure everything that isn't captured by only asking questions of a portion of the population.

Adding and subtracting a margin of error from its estimate gives you a range within which the actual number is likely to fall. Census Bureau data is published at the 90% confidence level, meaning that nine times out of ten, the true value will fall somewhere within the range you've created around the estimate (by adding and subtracting the margin of error).