TABLE 2. Time of Detected Population Response to COVID-19 and Related Npis in Each City.
| City | First case | Shelter-in-place order | Early warning (Essential POIs) | Early warning (Non-essential POIs) | Response-case lag* | Response-policy lag* | Essential-non-essential lag* |
|---|---|---|---|---|---|---|---|
| Austin | Mar-13 | Mar-24 | Feb-23~25 | Mar-2~4 | 19 | 30 | 8 |
| Charlotte | Mar-3 | Mar-24 | Feb-27~29 | Mar-13~15 | 5 | 26 | 15 |
| Chicago | Jan-24 | Mar-21 | Feb-27~29 | Mar-4~6 | −34 | 23 | 6 |
| Dallas | Mar-10 | Mar-23 | Feb-26~28 | Feb-26~28 | 13 | 26 | 0 |
| Detroit | Feb-25 | Mar-24 | Mar-1~3 | Mar-4~6 | −5 | 23 | 3 |
| Fort Worth | Mar-10 | Mar-23 | Mar-11~13 | Mar-14~16 | −1 | 12 | 3 |
| Houston | Mar-4 | Mar-24 | Feb-29~Mar-2 | Mar-1~3 | 4 | 24 | 1 |
| Jacksonville | Mar-12 | Apr-2 | Feb-27~29 | Mar-14~16 | 14 | 35 | 16 |
| Los Angeles | Jan-26 | Mar-19 | Feb-14~16 | Mar-13~15 | −19 | 34 | 28 |
| New York | Mar-1 | Mar-20 | Mar-2~4 | Mar-3~5 | −1 | 18 | 1 |
| Philadelphia | Mar-10 | Mar-23 | Feb-26~28 | Mar-14~16 | 13 | 26 | 17 |
| Phoenix | Jan-26 | Mar-31 | Feb-26~28 | Mar-14~16 | −31 | 34 | 17 |
| San Antonio | Mar-13 | Mar-24 | Feb-26~28 | Mar-8~10 | 16 | 27 | 11 |
| San Diego | Feb-14 | Mar-19 | Feb-24~26 | Mar-14~16 | −10 | 24 | 19 |
| San Francisco | Mar-5 | Mar-19 | Mar-7~9 | Mar-8~10 | −2 | 12 | 1 |
| San Jose | Jan-24 | Mar-19 | Feb-24~26 | Mar-9~11 | −31 | 24 | 14 |
| Seattle | Jan-21 | Mar-23 | Feb-29~Mar-2 | Feb-29~Mar-2 | −39 | 23 | 0 |
*
Note: Negative value means early-warning signals were detected later than the dates of first confirmed cases and shelter-in-place orders; positive value represents early-warning signals were detected earlier. We used the earlier dates between early-warning signals for essential and non-essential POIs to determine the response-case lag and response-policy lag. Unit of time lags: days.