Skip Navigation

U.S. State and County Estimates

NCES has produced estimates of adults’ literacy and numeracy skills for all U.S. states and counties, which are accessible through an interactive mapping tool:

U.S. PIAAC Skills Map: State and County Indicators of Adult Literacy and Numeracy

For all 50 U.S. states, all 3,141 U.S. counties, and the District of Columbia, the Skills Map provides four different estimates of the literacy and numeracy proficiency of adults (aged 16–74):

  1. the percentage with the lowest levels of proficiency (at or below Level 1; below 226 points),
  2. the percentage with medium proficiency (at Level 2; 226–275 points),
  3. the percentage with the highest levels of proficiency (at or above Level 3; above 275 points), and
  4. the average score for all adults (aged 16–74) in the state or county (on the PIAAC scale of 0–500).

For more information about PIAAC proficiency levels, visit Literacy Proficiency Levels and Numeracy Proficiency Levels.

The Skills Map allows users to compare the estimates of any county to those of its state or compare the estimates of any state to the national estimates. It also allows users to compare the estimates for any two counties or for any two states.

In order to help users to better understand the results produced for each state or county, the skills map gives users access to selected demographic variables from the American Community Survey (ACS). The available ACS variables provide context for the estimates by presenting basic demographic characteristics for the state or county, such as educational attainment, race/ethnicity, nativity, employment status, and poverty level.

These state and county estimates are based on combined PIAAC data collected in 2012, 2014, and 2017, and are produced using an advanced statistical method generally referred to as small area estimation (SAE). SAE is a model-dependent approach that produces indirect estimates for geographic areas where survey data are inadequate for direct estimation. For more information about the SAE technique and the development of these estimates, please refer to the methodology report.



State & County Estimates FAQs


1. What are the differences between U.S. PIAAC State and County estimates and previously published PIAAC estimates?

The previously published PIAAC estimates were computed directly using PIAAC survey data. Those estimates are representative of the national household population or large subgroups of the national household population. Unlike the previously published PIAAC estimates, U.S. PIAAC State and County estimates are model based, using a statistical technique called small area estimation (SAE) to provide valid estimates for U.S. states and counties. SAE refers to a variety of methods to estimate information for subpopulations or smaller areas of interest. SAE uses survey data, in combination with correlated data at the small-area level from other sources, to model the estimates of interest. In this case, the small areas are states and counties in the United States and the estimates of interest are skills proficiencies of the population.

The model-dependent approach was used to produce estimates for states and counties, for which PIAAC sample sizes were too small for direct estimation. The models used the combined 2012/2014/2017 U.S. PIAAC data in conjunction with data from the U.S. Census Bureau's American Community Survey (ACS, 2013-2017) to produce reliable estimates. The estimates are thus predictions of how the adults in the whole state or county would have performed had they been administered the PIAAC assessment.

The U.S. PIAAC State and County estimates are not directly comparable to the previously published PIAAC estimates for the United States because of the following differences:

  1. The U.S. PIAAC State and County data are from the combined 2012/2014/2017 data collections whereas the previously published PIAAC estimates are for either 2012/14 or 2017.
  2. The average scores and proficiency levels include the literacy-related non-respondents (adults whose English language skills were too low to participate in the study) whereas the previous PIAAC estimates exclude them. The U.S. PIAAC State and County estimates assume this population as performing at or below Level 1 for proficiency levels.
  3. The national-level estimates in the PIAAC Skills Map are weighted aggregates (based on the population of the counties) of the county-level estimates.

The PIAAC State and County estimates are likewise not directly comparable to previous PIAAC estimates in international reports published by the Organization for Economic Co-operation and Development (OECD) for the following reasons:

  1. The target population for U.S. reporting was 16- to 74-year-olds whereas the OECD published results for 16- to 65-year-olds.
  2. The U.S. average scores and proficiency levels include the literacy-related non-respondents whereas the OECD international reporting exclude them.

Top


2. How are U.S. PIAAC State and County estimates reported?

The U.S. PIAAC State- and County-level estimates are reported for both literacy and numeracy for the percentage of the population at or below Level 1 (low proficiency), the percentage of the population at Level 2 (medium proficiency), and the percentage of the population at or above Level 3 (high proficiency), as well as the average scale score for the population in a county or a state. The table below provides definitions for the proficiency levels.

U.S. PIAAC Proficiency Measures Literacy Numeracy
At or below Level 1
0–225 points
Adults at this level can be considered at risk for difficulties using or comprehending print material. Adults at the upper end of this level can read short texts, in print or online, and understand the meaning well enough to perform simple tasks, such as filling out a short form, but drawing inferences or combining multiple sources of text may be too difficult. Adults who are below Level 1 may only be able to understand very basic vocabulary or find very specific information on a familiar topic. Some adults below Level 1 may struggle even to do this and may be functionally illiterate. Adults at this level can be considered at risk for difficulties with numeracy. Adults at the upper end of this level can understand how to add, subtract, multiply, and divide and can perform basic one-step mathematical operations with given values or common spatial representations (e.g., calculate how many bottles of soda are in a full box with two levels when only the top level can be seen). Adults who are below Level 1 may only be able to count, sort, and do basic arithmetic operations with simple whole numbers and may be functionally innumerate.
Level 2
226–275 points
Adults at this level can be considered nearing proficiency but still struggling to perform tasks with text-based information. Such adults may be able to read print and digital texts, relate multiple pieces of information within or across a couple documents, compare and contrast, and draw simple inferences. They can navigate in a digital environment to access key information, such as finding two main benefits of one product over another. However, more complex inferencing and evaluation may be too difficult. Adults at this level can be considered nearing proficiency but still struggling to perform numeracy tasks. Such adults can successfully perform tasks requiring two or three steps involving calculations with whole numbers and common decimals, percentages, and fractions. They can conduct simple measurement and interpret relatively simple data and statistics in texts, tables, and graphs. However, more complicated problem solving (where the information is not explicit or is in an unfamiliar context) may be too difficult.
At or above Level 3
276 points or more
Adults at these levels can be considered proficient at working with information and ideas in texts. They have a range of higher literacy skills from the ability to understand, interpret, and synthesize information across multiple, complex texts to the ability to evaluate the reliability of sources and infer sophisticated meanings and complex ideas from written sources. Adults at these levels can be considered proficient at working with mathematical information and ideas. They have a range of numeracy skills from the ability to recognize mathematical relationships and apply proportions to the ability to understand abstract representations of mathematical concepts and engage in complex reasoning about quantities and data.

Top


3. What statistical models are used for the U.S. PIAAC small area estimation?

The U.S. PIAAC State and County estimates are based on area-level Hierarchical Bayes linear threefold models. A bivariate model was fit for the percentages at or below Level 1 and at or above Level 3, which were then used to derive the percentage at Level 2. A univariate model was fit for the average. Separate models were produced for literacy and numeracy. All models include three levels of random effects: county, state, and census division. Each model used the following seven county-level covariates:

  • Percentage of population aged 25 and over with less than high school education;
  • Percentage of population aged 25 and over with more than high school education;
  • Percentage of population below 100 percent of the poverty line;
  • Percentage of Black or African American population;
  • Percentage of Hispanic population;
  • Percentage of civilian noninstitutionalized population who have no health insurance coverage; and
  • Percentage of population aged 16 and over with service occupations.

The source for these covariates was the Census Bureau's American Community Survey 2013–2017 data. Further details are provided in the PIAAC State and County Estimation Methodology Report.

Top


4. Can the U.S. PIAAC State and County estimates be compared to the previously reported PIAAC estimates for other countries or OECD/international averages?

The U.S. PIAAC State and County estimates are not measuring the same population as the previous estimates for PIAAC countries that are reported by the OECD. Specifically, the U.S. PIAAC State and County estimates (1) represent adults aged 16 to 74, whereas the OECD's estimates for participating countries represent adults aged 16 to 65, and (2) include “literacy-related non-response” (i.e., adults whose English language skills were too low to participate in the study), whereas the OECD's estimates for countries exclude this group.

Top


5. Are there other survey programs that have used small area estimation (SAE) to produce indirect estimates?

A number of federal statistical agencies have developed SAE methods and have published SAE estimates. For example, the Census Bureau's Small Area Income and Poverty Estimates (SAIPE) provides annual estimates of income and poverty for states, counties, and school districts. Indirect estimates are also produced for the National Survey on Drug Use and Health. Other examples can be found in Czajka, Sukasih, and Maccarone (2014). For more information on the PIAAC State and County estimates, please go to Program for the International Assessment of Adult Competencies (PIAAC): State and County Estimation Methodology Report (NCES 2020-225).

Top


6. How do we know that the U.S. PIAAC State and County estimates are valid?

The PIAAC SAE program employed an extensive model evaluation process, as models are never a perfect fit to the data and systematic errors can manifest themselves. It was especially important for PIAAC to conduct a thorough evaluation of the model development because over 90 percent of the county estimates rely solely on the model predictions. A full range of model diagnostics, sensitivity analysis, and evaluation were conducted. For example, the model predictions were compared to direct estimates. Model predictions were generally close to direct estimates for counties with the largest PIAAC sample sizes, as one would expect for valid models. In addition, the modeling approach improved on the associated statistical error; for instance, the standard error of model predictions was substantially smaller than the standard error of direct estimates. The evaluation results confirmed the validity of the U.S. PIAAC State and County estimates.

Top


7. What is the level of precision for the U.S. PIAAC State and County estimates?

Overall, the state-level estimates are more precise than the county-level estimates, and, to a lesser extent, the estimates are more precise in counties and states that had persons sampled in the PIAAC household sample than in those that had no persons sampled.

The coefficient of variation (CV) is a common way of measuring precision. CVs for the county-level estimates for the percentage at or below Level 1 in literacy have a median CV of 10 percent. Estimates with CVs of this magnitude are considered to be precise (i.e., at a high confidence level). Meanwhile, there are a small number of county estimates that have CVs larger than 50 percent, which are imprecise and indicated as low confidence estimates in the U.S. PIAAC Skills Map. The state predictions are more precise, with a median CV of 8.1 percent.

Another way of measuring precision is to report credible intervals. For example, for the percentage at or below Level 1 in literacy, the median credible interval width for county estimates is 8.0 percentage points, while for the state estimates the median is 6.1 percentage points. The median credible interval width is 7.2 percentage points for county estimates that had persons in the PIAAC 2012/2014/2017 household sample and 8.0 percentage points for county estimates that had no persons in the PIAAC household sample.

The accuracy level for the other five types of percentage estimates (i.e., the percentage at Level 2, the percentage at or above Level 3 in literacy, and the three percentages in numeracy) is similar to that for the percentage at or below Level 1 in literacy, with slightly larger credible intervals and slightly smaller CVs.

Top


8. Can I get U.S. PIAAC State and County estimates in a data file?

Yes. The estimates are available for download in the U.S. PIAAC Skills Map. See the last link on the left-hand navigation of the Skills Map (click the button “Download Data” under the bigger button “Compare Counties”). To access the Skills Map, please visit https://nces.ed.gov/surveys/piaac/skillsmap.

Top


9. How are the comparisons made in the U.S. PIAAC Skills Map?

The U.S. PIAAC Skills Map can make comparisons of two areas at a time. For example, a county can be compared to another county or to the state it is in, or a state could be compared to another state or to the nation as a whole. For a given pair of areas—(county1, county2) or (county1, state1) or (state1, state2) or (state1, nation)—the hypothesis testing of the difference between the two areas being equal to zero is performed for all eight measures (percentages of the area's populations at or below Level 1, at Level 2, and at or above Level 3, as well as average scores in both literacy and numeracy domains).

The results are reported as “statistically” different when differences are significant at the critical significance level that was adjusted using the Bonferroni method, an adjustment to account for the additional statistical error that occurs when multiple comparisons are conducted simultaneously. The results are reported as “notably” different when differences that are not significant under the Bonferroni-adjusted critical significance level are significant under a single test at the α (type 1 error) = 0.05 level.

Top


10. Why are U.S. PIAAC State and County estimates not presented for Problem Solving in Technology-Rich Environments (PS-TRE) skills?

Reporting on PS-TRE skills is problematic at the county level because the percentage of people who completed PIAAC on a computer is likely to vary widely across counties. It could be misleading to compare average PS-TRE scores or the percentage of the population at a certain PS-TRE proficiency level, because they may represent different percentages of the population as well as different populations (e.g., just the most computer savvy in one county versus a cross-section of computer users in another). Without knowing whether 90 percent or 15 percent of a county's population completed the assessment on a computer, a score of, say, 500 is both not meaningful and misleading. While respondents were encouraged to use the computer for the assessment if they were able, the percentage using the computer could be influenced by personal preference as well. Therefore, the meaning of the percentage at each proficiency level is also influenced by the percentage of respondents who used the computer to complete the assessment. In addition, complete covariance information is not available for respondents who did not use the computer for the assessment. The estimates of PS-TRE performance also have large standard errors that depend on estimates of computer use per county, which also have large standard errors that need to be factored in. For these reasons, it was determined that PS-TRE was not a solid domain for reporting state- and county-level estimates.

Top


11. How do NAAL State and County estimates differ from U.S. PIAAC State and County estimates? Are they comparable?

The proficiency assessment instruments and scales used in the 2003 National Assessment of Adult Literacy (NAAL) and the 1992 National Adult Literacy Survey (NALS) were different from those used in PIAAC, and thus the estimates for counties and states from NAAL and NALS SAE are not comparable to the corresponding estimates from PIAAC. The table below summarizes other differences between NAAL and PIAAC State and County estimates.

NAAL and NALS State and County Estimates U.S. PIAAC State and County Estimates
Age range 16 years and older 16- to 74-year-olds
Estimates Percentage of adults lacking Basic prose literacy skills For literacy and numeracy separately:
  • Percentage of the population at or below Level 1
  • Percentage of the population at Level 2
  • Percentage of the population at or above Level 3
  • Average scale score
Covariates used in SAE model 2003 NAAL model:
  • Percentage of population who were foreign born and had stayed in the United States for 20 years or less
  • Percentage of population aged 25 and older with a high school education or less
  • Percentage of population who were Black or African American, or Hispanic
  • Percentage of population in households with incomes below 150% of poverty level
  • Indicator variable identifying the New England and North Central census divisions
  • Indicator variable identifying the SAAL states
1992 NALS model:
  • Percentage of population for whom English was not a native language
  • Percentage of population aged 25 and older with only a high school education or less
  • Percentage of population who were Black or African American
  • Percentage of population who were Hispanic
  • Indicator variables identifying the New England and North Central census divisions
  • Indicator variable for counties in a SALS state.
PIAAC model:
  • Percentage of population aged 25 and older with less than a high school education
  • Percentage of population aged 25 and older with more than a high school education
  • Percentage of population below 100% of the poverty line
  • Percentage of population who were Black or African American
  • Percentage of population who were Hispanic
  • Percentage of civilian noninstitutionalized population who have no health insurance coverage
  • Percentage of population aged 16 and older with service occupations

NOTES: NAAL, National Assessment of Adult Literacy; NALS, National Adult Literacy Survey; PIAAC, Program for the International Assessment of Adult Competencies; SAAL, State Assessment of Adult Literacy; SALS, State Adult Literacy Survey

Top