Table 1. Demographic characteristics of the study population.
| Pre-Pandemic* | Pandemic* | Standardized Mean Difference** | |
|---|---|---|---|
| n | 7,048,075 | 3,387,469 | |
| Female | 48.9% | 48.9% | 0.00 |
| Age | |||
| < 1 | 2.2% | 2.1% | -0.04 |
| 1–5 | 25.9% | 25.6% | -0.01 |
| 6–12 | 40.6% | 40.4% | -0.01 |
| 13–17 | 31.3% | 31.9% | 0.02 |
| Race/Ethnicity (excluding unknown) | |||
| non-Hispanic White | 69.7% | 70.5% | 0.04 |
| non-Hispanic Black | 8.1% | 7.9% | -0.04 |
| Hispanic | 15% | 14.4% | -0.05 |
| Asian | 7.2% | 7.2% | 0.01 |
| Unknown Race/Ethnicity | 16.5% | 42.3% | - |
| Census Region | |||
| New England | 2.5% | 2.8% | 0.09 |
| Middle Atlantic | 6.4% | 6.4% | 0.00 |
| East North Central | 15.2% | 15.6% | 0.03 |
| West North Central | 11.4% | 13% | 0.15 |
| South Atlantic | 20% | 20.4% | 0.03 |
| East South Central | 3.7% | 3.8% | 0.03 |
| West South Central | 17.5% | 15.7% | -0.13 |
| Mountain | 10.9% | 10.8% | -0.01 |
| Pacific | 12.4% | 11.6% | -0.07 |
| Income quartile (of patient zip code) | |||
| Lowest (< $55,019) | 21.8% | 21% | -0.04 |
| Second ($55,020 - $72,759) | 25.1% | 25.1% | 0.00 |
| Third ($72,759 - $96,969) | 26.7% | 27% | 0.02 |
| Highest (> $96,969) | 26.5% | 26.8% | 0.02 |
*Pre-pandemic period corresponds to January 2016 until mid-March 2020. Pandemic period corresponds to mid-March 2020 through March 2021.
**Standardized mean differences can be interpreted using Cohen’s guideline: d = 0.2 corresponds to a small difference; d = 0.5, to a medium difference; and d = 0.8 to a large difference.