The household characteristics score is one of four component scores that combined form the overall Social Vulnerability Index (SVI). This component score measures the following household factors at the level of a participant's Census tract:

1. population aged 65 and older
2. population aged 17 or younger
3. population of those with disabilities
4. amount of single parent households

Component scores are percentage percentiles. These are created by first calculating a component score as a percentage for its census tract. That percentage is then ranked against all other tract percentages and assigned a percentile ranking.

Score ranges from 0.00 (least vulnerable) to 1.00 (most vulnerable) with a higher score reflecting a more vulnerable Census tract for a given participant’s address.

Participants' study visit year is used to determine the year of SVI data linked to their geocoded address. The first year that a valid address is available to be geocoded for a participant once enrolled in the parent study is referred to as the participant's "geocoded baseline (GBL)". GBL is the same as parent study baseline for all participants except for some AACore participants for which address was not collected at the time of parent study enrollment.