- Metric Name:  Poverty Percentile

- Data Vintage:  2021

- Unit Of Measure: percentile

Percent of population living below two times the federal poverty level. The U.S. Census Bureau determines the federal poverty level each year. The poverty level is based on the size of the household and the age of family members. If a person or family’s total income before taxes is less than the poverty level, the person or family are considered in poverty. Many studies have found that people living in poverty are more likely than others to become ill from pollution.

Creation Method: CalEnviroScreen, Version 4.0, is a science-based method for identifying impacted communities by taking into consideration pollution exposure and its effects, as well as health and socioeconomic status, at the census-tract level. CalEnviroScreen 4.0 uses the census tract as the unit of analysis. Census tract boundaries are available from the Census Bureau. CalEnviroScreen uses the Bureau’s 2010 boundaries. New boundaries will be drawn by the Census Bureau as part of the 2020 Census but will not be available until after 2022. OEHHA will address updates to census tract geography in CalEnviroScreen at that time. There are approximately 8,000 census tracts in California, representing a relatively fine scale of analysis. Census tracts are made up of multiple census blocks, which are the smallest geographic unit for which population data are available. Some census blocks have no people residing in them (unpopulated blocks).

The poverty percentile is derived from

- The 2015-2019 American Community Survey, a dataset containing the number of individuals below 200 percent of the federal poverty level was downloaded by census tracts for the state of California.

- The number of individuals below 200% of the poverty level was divided by the total population for whom poverty status was determined.

- Unlike the US Census, ACS estimates come from a sample of the population and may be unreliable if they are based on a small sample or population size. The standard error (SE) and relative standard error (RSE) were used to evaluate the reliability of each estimate.

- The SE was calculated for each census tract using the formula for approximating the SE of proportions provided by the ACS (American Community Survey Office, 2013, pg. 13, equation 4). CalEnviroScreen 4.0 189 When this approximation could not be used, the formula for approximating the SE of ratios (equation 3) was used instead.

- The RSE is calculated by dividing a tract’s SE by its estimate of the percentage of the population living below twice the federal poverty level, and taking the absolute value of the result.

- Census tract estimates that met either of the following criteria were considered reliable and included in the analysis:

- RSE less than 50 (meaning the SE was less than half of the estimate) OR

- SE was less than the mean SE of all California census tract estimates for poverty.

- Census tracts with unreliable estimates received no score for the indicator (null). The indicator was not factored into that tract’s overall CalEnviroScreen score.

- Census tracts that met the inclusion criteria were sorted and assigned percentiles based on their position in the distribution.

- Credits:  California Environmental Protection Agency, CalEnviroScreen 4.0

Office of Environmental Health Hazard Assessment, CAL EPA: 
Data disclaimer:  
The State makes no claims, promises, or guarantees about the accuracy, completeness, reliability, or adequacy of these data and expressly disclaims liability for errors and omissions in these data. No warranty of any kind, implied, expressed, or statutory, including but not limited to the warranties of non-infringement of third party rights, title, merchantability, fitness for a particular purpose, and freedom from computer virus, is given with respect to these data.