- Data sources and screenshots for California
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- Last updated March 7, 2021 2:59 am ET
Data Reporting Assessment (Learn more about data quality assessments)
- Serious issues exist for state-level metrics
- Few issues exist for race and ethnicity data
- Few issues exist for long-term-care data
When California reports no data, several days of data, or unusual data (such as decreases in values that should increase), our volunteers note it here on the date the anomaly occurred. We also note here changes in our own methodology that affect the data.
On February 25, 2021, California announced that their deaths included a backlog of 806 deaths initially not reported as COVID-19 deaths from Los Angeles County. As a result, many of the deaths reported on February 25, 2021 occurred between December 3, 2020 and February 3, 2021. We urge caution when interpreting numbers from this period, and encourage the use of 7 and 14-day averages as more reliable metrics than individual figures.
On December 16, 2020, California announced that their cases for December 16, 2020 include 15,337 cases from previous days due to a change in case processing. It appears this new process will regularly include a higher volume of cases that were not identified within the previous 24 hours.
As of September 18, 2020, California's total test results are drawn from our
totalTestsViral field instead of calculated via positive+negative.
From July 23 through July 28, 2020, California reported that its Now hospitalized and Now in ICU were incomplete due to its transition to the HHS reporting system. We carried over hospitalization figures until July 28. We will backfill the complete numbers for this period if the complete data becomes available.
From June 29 to July 5, 2020, California made revisions to daily case numbers. On July 17, we updated the values based on the most recent data from the state dashboard.
On July 8, 2020, California data included a backlog from Los Angeles County, which had not reported for several days. Approximately 1,000 of the 11,000 new cases were attributed to this backlog data.
As of April 22, 2020, California has reported specimens tested instead of people tested. Because some people may be tested more than once, this number is probably higher than the number of people tested.
On April 4 and April 22, 2020, California reported large batches of backlogged negative test data.
Prior to April 1, 2020, we used county data sources for more reliably timely reporting of California's COVID-19 data. At the start of April, we began reporting primarily from the state data dashboard(s). This led to a modest drop in cases and deaths, as the state's data lags behind the county sources.