# Share of days with good air quality (US EPA AQI) in Simpson County

Share of days with good air quality (US EPA AQI) in Simpson County was 93.4% in 2025. Source: U.S. Environmental Protection Agency.

- Indicator id: `aqi_good_days_share`
- Place id: `us-county-21213`
- Unit: %
- Definition: Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.
- Note: United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.
- Source: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Retrieved: 2026-10-12
- License: Public domain (US government work, 17 U.S.C. 105); citation requested
- Citation: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
- Web page: https://invokely.ai/en/good-air-quality-days-share/simpson-county-kentucky
- API: https://invokely.ai/api/v1/series?indicator=aqi_good_days_share&place=us-county-21213

| Period | % |
|---|---:|
| 2025 | 93.4 |
| 2024 | 84.3 |
| 2023 | 83.6 |
| 2022 | 90 |
| 2021 | 91.4 |
| 2020 | 98.2 |
| 2019 | 91 |
| 2018 | 87.2 |
| 2017 | 92.8 |
| 2016 | 89.3 |
| 2015 | 86.1 |
| 2014 | 88.6 |
| 2013 | 94.5 |
| 2012 | 80.3 |
| 2011 | 68 |
| 2010 | 65.8 |
| 2009 | 81.6 |
| 2008 | 65.3 |
| 2007 | 50.6 |
| 2006 | 72.4 |
| 2005 | 61.2 |
| 2004 | 74.7 |
| 2003 | 65.3 |
| 2002 | 71.4 |
| 2001 | 64.5 |
| 2000 | 66 |
| 1999 | 61.9 |
| 1998 | 68.2 |
| 1997 | 74.8 |
| 1996 | 74.1 |
| 1995 | 66.7 |
| 1994 | 77.5 |
| 1993 | 82.6 |
| 1992 | 83.5 |
| 1991 | 67.2 |