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Comparing state, county metrics for COVID-19 a confusing exercise
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Comparing state, county metrics for COVID-19 a confusing exercise

Capture of state's county metrics chart as of 6.19

A portion of the June 19 state's metrics chart for counties, including Santa Barbara County in blue and San Luis Obispo County in red, shows the data for, from left, seven-day average number of tests per day; cases per 100,000 over 14 days; seven-day average percentage of positive tests; three-day average of percentage change in hospitalization; percentage of ICU beds available; and percentage of ventilators available.

If you’ve wondered why the numbers on Santa Barbara County’s COVID-19 metrics webpage don’t match the state's numbers the same day on its page, you’re not alone.

And sometimes, the numbers reported on the state and county websites don’t even match the data provided that day by County Public Health Department officials during press briefings and the weekly COVID-19 status report to the Board of Supervisors.

There are several reasons for the discrepancies.

The different numbers don’t mean one site is right and the other wrong; the discrepancies are caused by the state and county using different reporting periods, expressing statistics differently, time lags for certain metrics, and updates being done at different times.

The state uses elevated disease transmission, increasing hospitalizations and limited hospital capacity as metrics to determine whether a county can move to the next stage in reopening the economy, must remain at the current stage or even step back to the previous stage, according to the County Department of Public Health’s Epidemiology Unit.

And even though the data don’t always match, the websites provide a way for the public to see if the county is meeting state requirements and compare Santa Barbara County’s status to that of other counties.

“There are some nuances to the data that [California Department of Public Health] is collecting and analyzing that may make it hard to replicate without having full access to background data,” said Timothy Watts, of the County Emergency Operations Center Joint Information Center public information staff.

“In terms of why different date periods are used, this is to help account for lag time in reporting,” Watts said.

The state website notes testing volume and testing positivity metrics have a seven-day lag, and hospitalization data can lag as much as two weeks.

It also says disease transmission and increasing hospitalization data were provided from a different range of time than what the state requested for variance attestations, although it doesn’t specify those different dates.

The metrics for “Increasing Hospitalization” provide an example of the difficulty of comparing the data on the state and county metrics websites.

According to the California Department of Public Health, if the three-day average of hospitalized COVID-19 patients in a county is more than 10% higher than the average for the previous three days, that county’s hospitalization rate is higher than what’s allowed.

On June 22, the state showed Santa Barbara County with a “three-day average” increase of 14.5%, thereby exceeding the allowable increase.

But the county’s website lists the required metric as a “seven-day average of daily percent change of less than 5%.”

The county provided daily percentage changes, with the most recent seven days, starting June 15, showing increases of 1.8%, 5.2%, 1.6%, 6.5% and 7.6%, then a decrease of 2.8% and finally a 0% change on June 21.

And even though the state says its data for hospitalization can lag by two weeks, the differences in the stated required metrics and the way the data are presented make comparing the two difficult, if not impossible, for the average citizen.

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County Reporter/Associate Editor

Lee Central Coast Newspapers associate editor Mike Hodgson covers Santa Barbara County government and events and issues in Santa Ynez Valley. Follow him on Twitter @MHodgsonSYVNews.

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