State Metrics (7 Day Avg and Lag)
Substantial (Tier 2)
Daily Case Rate
Test Positive %
Moving Through Tiers
- CDPH will assess indicators weekly. The first weekly assessment will be released on September 8, 2020.
- A county will remain in a tier for a minimum of three weeks before being able to advance to a later tier.
- A county can only move forward one tier at a time, even if metrics qualify for a more advanced tier.
- If a county's case rate and test positivity measure fall into two different tiers, the county will be assigned to the more restrictive tier.
- City local health jurisdiction (LHJ) data will be included in overall metrics, and city LHJs will be assigned the same tier as the surrounding county.
- A county must have been in the current tier for a minimum of three weeks, except as described in the "Initial step applied on August 28, 2020" section above.
- A county must meet criteria for the next tier for both measures for the prior two consecutive weeks in order to progress to the next tier.
- In addition, the state will establish health equity measures on activities such as data collection, testing access, contact tracing, supportive isolation, and outreach that demonstrate a county's ability to address the most impacted communities within a county. Additional measures addressing health outcomes such as case rates, hospitalizations and deaths, will also be developed and tracked for improvement.
- During the weekly assessment, if a county's adjusted case rate and/or test positivity has been within a more restrictive tier for two consecutive weekly periods, the county must revert to the more restrictive tier.
- At any time, state and county public health officials may work together to determine targeted interventions or county wide modifications necessary to address impacted hospital capacity and drivers of disease transmission, as needed.
- Counties will have three days to implement any sector changes or closures unless extreme circumstances merit immediate action.
MethodologyCounties are assigned a tier based on two metrics: test positivity and case rate. The case rate is adjusted based on testing volume per 100,000 population as described below. Due to variability in data, this adjustment does not apply to small counties (defined as those with a population less than ~100,000 residents)
- Calculated as the case rate multiplied by a case rate adjustment factor that is based on the difference between the county testing volume (testing volume, tests per 100,000 per day, described below) and the median testing volume calculated across all counties. The median testing volume thus forms an anchor for this adjustment and is recalculated every four weeks to prevent undue fluctuation while remaining sensitive to evolving testing trends.
- Case rate will be determined using cases confirmed by PCR
- For counties with a testing volume above the median, the adjustment factor is less than 1, decreasing in a linear manner from 1.0 to 0.6 as testing volume increases from the anchor point to 2x that value. The adjustment factor remains at 0.6 if the county testing volume is greater than 2x the state median.
- For counties with a testing volume below the state median, the adjustment factor is greater than 1, increasing in a linear manner from 1.0 to 1.4 as county testing volume decreases from the state median to zero.
- The linear adjustment formula can be expressed mathematically as follows: 1-(((county testing rate – state median testing rate)/state median testing rate) * 0.4)