Table 2.

Percentage Differences in Potential Confounders at Baseline and Before and After Weighting

Baseline characteristics	Before weighting (% difference)	After weighting (% difference)
Age at enrolment (years), category
20–29	1	5
30–39	18	− 1
40–49	− 5	− 3
50–59	− 9	2
≥ 60	− 6	− 2
Female	− 10	3
White, non-Latinx	21	0
Unstable housing	5	0
Living outdoors	14	4
Injected opioids, past 30 days	8	0
Non-injection use of opioids, past 30 days	− 3	0
Daily alcohol use, past 30 days	− 6	− 3
Ever enrolled in a treatment programme	14	5
Currently enrolled in a treatment programme	− 10	0
Income from illegal activities	22	− 2
Psychiatric illness diagnosis	− 5	− 1
Ever used drugs in bathroom of service agency	15	− 3

% difference = those who used the safe consumption site in 6 months prior to enrolment − those who did not use the site in 6 months prior to enrolment. Positive values indicate greater frequency of a covariate (or category) among people using the safe consumption site compared to those not using the safe consumption site at enrolment