The reason is in the way the counties dealt with equity in health.
California relies mainly on two metrics to lay counties in colored layers that determine local reopening guidelines, such as when restaurants can resume indoor dining. The two main metrics are positive test rates and daily cases per 100,000 residents; the latter is adjusted based on how many tests a county is doing.
To move from the purple layer to the red layer, counties must report positive test rates of 8% or less and adjusted cased rates of 7 or less. And they must report these red layer numbers for two consecutive weeks.
But the state also follows a third metric called health equity score. This score is the positive test rate for low-income or otherwise disadvantaged neighborhoods. The scoring aims to measure how well the counties are handling the pandemic in communities that have been most difficult. It also encourages counties to address health inequities by rewarding signs of progress.
The state allows counties to move from the purple layer to the red layer if their health equity score is two levels higher – the orange layer – for two consecutive weeks. In fact, counties can move to the red level, even though their other data is still at the purple level, but the health equity score is low.
Marin and San Mateo counties have reported health equity scores below 5% – the limit for the orange level – for two consecutive weeks starting on Tuesday. They were the only counties in the Bay Area to do that. Marin County is reporting rates for the purple layer – 7.4 cases per 100,000 residents – but has still been allowed to switch to the red layer.
San Francisco’s health equity score does not meet this criterion: it reported a score in the orange layer this week (4.2%), but in the red layer the previous week (5.4%). That’s why San Francisco will have to wait another week to get out of the purple layer.
Erin Allday is a writer for the San Francisco Chronicle. Email: [email protected] Twitter: @erinallday