Methods

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Data Definitions

Census Block — A census block is the smallest geographic unit used by the US Census Bureau for the tabulation of data. Multiple blocks make up one census block-group.

Census Block Group — A census block-group averages 1,500 residents and is the next largest unit after a block, and smaller than a tract. Block-group is the smallest geography for which the bureau publishes data on poverty, median household income, and other sample data attributes.

Census Tract — Census tracts average 4,000 residents and are a larger unit than a census block-group.

No population areas — Census blocks with no population, per the Decennial Census (P1)

Parks — Open space land available for the general public, it includes a formal recreation destination or facility. See the 2015 SCORP, "Understanding park and Open Space Data", for more information about what is and is not counted as open space recreation land for the purpose of these SCORP tools.

Parks and park acres are based on best available source information but may not always contain exact boundaries or all parks in specific locations. Parks are further defined in this report: https://parksforcalifornia.org/park_equity#parks_data

Park access — A calculation of the population living in close proximity to a park, using two approaches:

1. A half mile zone surrounds all parks. The population living within a half mile of a park is counted as being in close proximity of a park.
2. Park acreage per 1,000 residents within a census tract.

Parks and park acres are based on best available source information but may not always contain exact boundaries or all parks in specific locations. Parks are further defined in this report: https://parksforcalifornia.org/park_equity#parks_data

For more information about the use of these standards, see the 2015 SCORP, "California Develops New Tools to Assess Park Need".

Population — Block and block-group population from Decennial Census (P1), American Community Survey 5-year estimates (B01001_001E)

Disadvantaged Community — Census block-groups with a Median HouseHold Income (MHHI) less than 80% of the California MHHI. The threshold is derived from American Community Survey 5-year estimates at the block-group geographic level, per the California Public Resources Code (PRC), Section 75005(g).

Severely Disadvantaged Community — Census block-groups with a Median Household Income (MHHI) less than 60% of the California MHHI. The threshold is derived from American Community Survey 5-year estimates at the block-group geographic level, per the California Public Resources Code (PRC), Section 75005(g).

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Data Sources

Census Blocks — 2010 and 2020 Decennial Census, 2010 and 2020 TIGER files

Census Block-Group, Census Tract — Block-group population estimates from the 2010 and 2020 Decennial Census, American Community Survey, and TIGER.

English Learner data— 2021-2022 school year, California Department of Education "fileselsch20.txt" 7MB Posted 7-Jan-2023; Data field: TOTAL_EL

Free or reduced price meals— 2021-2022 school year, California Department of Education "frpm2122.xlsx" 3MB Posted 7-Jan-2023; Data fields: Enrollment (K-12), FRPM Count (K-12), Percent (%) Eligible FRPM (K-12)

Parks — California Protected Areas Database (CPAD) adjusted for California State Parks

Schools— California School Campus Database (CSCD) 2021 and the California Department of Education "Public Schools and Districts", 11/2020

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The Community FactFinder (CFF) tool runs demographic summaries for a half mile radius of any point drawn in California. The demographic data is from the most current release of the Census Bureau's American Community 5-year survey. To operate, the program draws a half mile circle around the selected point. It then finds all of the block-groups that intersect with that radius. The intersected block-groups are split so that only the portion of the block-group polygons that are inside of the polygon are retained. While splitting the block-groups, the program assumes and equal distribution of population. Therefore, if only 1/3 of the block-group is inside of the radius, only 1/3 of the population is counted. The resulting full and partial block-groups are then summarized and reported.

While this method produces accurate results in urban areas, rural areas with small pocket populations can be improved. To improve rural area calculations, one needs to distribute the block-group data proportionally down to the census block level. This is done to avoid large geographic block-groups with a small populated portion from being over distributed. For example, a block-group covers 35 square miles with a population of 1,000. Inside that block-group there is one contiguous 5 square mile cluster with 900 people, the other 100 people are spread out over the remaining 30 square miles. By breaking the block-group geometry down to blocks one can more accurately place the population, and thus the park acreage per thousand residents and other attributes.

Each time a circle is identified the CFF tool reviews the block-groups overlapped by the circle. If any of the block-groups are classified as rural, the tool uses the block level allocated estimates for the attribute reporting. Circles do not mix block-group and block input methods – this avoids possible edge matching issues.

Overview of Methods and Data

Variables:
BG_ID = Block group ID (standard Census format)
SA_ac = Total acres in service area (sum of all BG_SA_ac values)
BG_ac = Acres of the full block-group
BG_SA_ac = Acres of block-group within the area
TotPop = Total population
PCI = Per capita income

Population is calculated as:
Population of Service Area = ∑ of [TotPop] *[BG_SA_ac]/[BG_ac]

Per Capita Income is calculated as:
Per Capita Income, Weighted Average = ∑ of ([BG_SA_ac] * [PCI])/ [SA_ac]

Sample:

Block Group ID	Block Group Acres	Acres of block-group within the area (BG_SA_ac)	Total Population	Per Capita Income (PCI)	Population of Service Area	BG_SA_ac * PCI
1	2.5	2.5	100	$50,000	100	$125,000
2	3	1.5	50	$100,000	25	$150,000

The area has a total of 4 "Acres of block-group within the area (BG_SA_ac)", a "Population of Service Area" of 125, resulting in a weighted Per Capita Income of $68,750.

Notes:

• Any attributes based on a count (people in poverty, race/ethnicity, etc.) are calculated with the same formula used for total population.
• Any attributes based on a value (median household income, etc.) are calculated with the same formula used for per capita income.
• The ACS reports a margin of error (MOE) for each statistic. Users should review and become familiar with the MOE. The Census Bureau provides a variety of resources online.
• The MOE does not reflect the error inherent in assuming equal distribution of an attribute across a block-group, or the error inherent in using a weighted average.

The map contains layers for Disadvantaged ($67,278) and Severely Disadvantaged ($50,458) communities. The thresholds are derived from the American Community Survey 2017-2021 (ACS 2017-21) 5-year estimates at the block group geographic level and the California State Median Household Income. Per the California Public Resources Code (PRC), Section 75005(g). ACS 2017-21 data is the most current data available and consistent with the demographics reported in the Community FactFinder tool.

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In addition to the statistics shown on the standard CFF application, the OEP site includes data on free/reduced meals and English language learners. Both data sets are from DataQuest, California Department of Education from the 2021-2022 school year.

School data is fetched for the nearest elementary, middle/junior/intermediate, and high school to the location the pin is dropped. The tool searches until it finds the nearest combination of three schools: one elementary, one middle/junior/intermediate, and one high school.

California schools are diverse in the types of schools and grade levels offered. For consistency, the OEP tool only includes traditional schools. Charter and magnet schools are not included.

Example 1

California State Parks - Outdoor Equity Program Report (Project ID: 104916)

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Example 2

California State Parks - Outdoor Equity Program Report (Project ID: 104922)

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Summary

With GIS tools, we created a half mile zone around all statewide parks. Using the most recent American Community Survey block-group population estimates, and an assumption of equal population distribution within block-groups, we then analyzed how many of California's 38 million residents live within, or outside of, the half mile zones surrounding all statewide parks.

Results: 21% of Californians, nearly 9 million people, live over a half mile from a park or open space. See an interactive map of results for the state, cities, counties, and districts on the Park Access Tool page

Overview of Methods and Data

Methods used to determine the population with or without close-to-home park access in California:

Classify all areas of the state as park, park access, or no park access:

1. Define "parks", as the CFF version of CPAD [defined above]
2. Buffer all parks by 1/2 mile to define "park access areas"
3. Define all non-park, and those areas outside the half mile buffer, as "no park access"
4. Erase areas: water, Department of Defense lands, block-groups with no population

Population Estimates:

1. Download the most recent block-group population figures (ACS 5-yr estimates) when a new SCORP is produced every five years
2. Erase the portion of block-groups that are water/bay
3. Assuming equal distribution of populations in block-groups, determine the number of people living in the three classifications:
1. Intersect the access types with the remaining block-groups
2. Calculate the percent of each block-group in each of the access types
3. Using the results of b., apply the same percent of the population to that access type.
EXAMPLE:
• Blockgroup acres: 500
• Park acres in block-group: 25
• Park access acres in block-group: 100
• No park access acres in block-group: 375
• Blockgroup population: 100
• In park access areas: 25
• In no park access areas: 75

The map contains layers for DAC and SDAC communities which were the threshold at the time the Park Access Tools were updated. The threshold is derived from American Community Survey 5-year estimates at the block-group geographic level and the California State Median Household Income. Per the California Public Resources Code (PRC), Section 75005(g). ACS 2014-18 data is consistent with the demographics reported in the Half Mile Access tool.

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Summary

California State Parks chose census tracts as the area against which to assess the amount of existing parkland in comparison to the 3 acres/1,000 population metric. Census tracts vary in population size, but average approximately 4,000 persons. Note that in some situations, additional parkland may lie at the edge of (or very close to) a particular tract, a condition not measured by this analysis.

Results: 61% of Californians live in census tracts with less than 3 acres/1,000 residents. See an interactive map of results for the state, cities, counties, and districts on the Park Access Tool page

Overview of Methods and Data

Methods used to determine the park acres per thousand residents, by census tract:

1. Intersect the census tracts with parks and open space
2. Recalculate the park acres for all park pieces cut up to tracts
3. Summary the total acres of park and open space in each tract
4. Calculate park acres per thousand residents for all tracts with population (tracts with no population were not calculated)

The map contains layers for DAC and SDAC communities which were the threshold at the time the Park Access Tools were updated. The threshold is derived from American Community Survey 5-year estimates at the block-group geographic level and the California State Median Household Income. Per the California Public Resources Code (PRC), Section 75005(g). ACS 2014-18 data is consistent with the demographics reported in the Parks per Thousand tool.

Park Access Tool Data was updated to inform California’s 2021-2025 SCORP. The next update will be released in 2024/25 to inform California's 2026-2030 SCORP.