In the decennial census and in the American Community Survey, the US Census Bureau asks respondents what language is spoken at home by each member of the household that is over 4 years old. The U.S. Census Bureau does not ask about data on language use by children younger than age 5 because it assumes that children at that age do not yet have a language. However, most children at that age are learning a language from their parents. To get an estimate of the number of children age 0 through 4 who speak a particular language or who are extremely likely to learn a particular language because their mother or father speaks that language, it is possible to use data on parental language.

The Census Bureau does not provide these data by most geographic regions. However, IPUMS provides these data by Public Use Microdata Areas (PUMAs).To estimate the child’s language using the parent’s language, it is necessary to match each child with his or her parents. This is not possible to do using the aggregate data tables available through American Factfinder but it is possible to do using the microdata available through the Integrated Public Use Microdata Series (IPUMS), publiched and maintained by the Minnesota Population Center. The IPUMS data are samples of censuses and the American Community Survey responses with weights attached to each response. Using the weights one can estimate the characteristics of the total population based on the sample of individual responses. Because they are individual responses, each child can be paired with the parent or parents he or she is living with and the characteristics of those parents. The responses, however, are not tied to the specific location of the household but are grouped into areas called Public Use Microdata Areas (PUMAs). These areas have a population of approximately 100,000 people and do not necessarily follow any particular political boundary. PUMAs can be grouped together to match the boundary of a county or a group of counties.

The question regarding the language spoken at home by each person on the American Community Survey questionnaire is a fill-in-the-blank style. This means that there is some inconsistency in the names of languages as one person may write Mandarin and another may write Chinese or one person may write Norwegian and another Scandinavian. In addition, allowing the respondent to fill in the language can lead to responses where the name of the language is unknown or nonsensical or even instances where the response box was left blank.

Languages most commonly spoken by children in Illinois

List of 30 languages most commonly spoken (or likely being learned) by children in Illinois.

Source of 2014 county data is ACS. All other data is from IPUMs.