Table 12.

SCS SROI sensitivity analyses.

Scenarios	Sensitivity analysis results
Scenario 1: Increasing the value of a human life proxy	A conservative proxy estimate of $22,229 QALY for the value of a human life was originally applied in the SROI model. However, a higher value of a statistical life (VSL) has been reported: $5,100,000 CAD, after adjusting for inflation (70). This increased the ratio from 4.44 to 851.49. Note: the 2007 VSL cost estimates reported by Chestnut and De Civita (70) ranged from $3.5 to 9.5 million CAD, which after being adjusted for inflation in 2025 increased to $5.1–13.9 million CAD. Our sensitivity analysis and subsequent ratio were calculated using the lower end of the reported range
Scenario 2: Increasing the value of a human life proxy and applying it to just one service user	The original model accounted for the number of service users who experienced the outcomes, based on available documentation. If the life of only one service user was helped, and the value of their life was estimated at $5,100,000 CAD, the ratio was 42.34
Scenario 3: Accounting for each outcome being experienced by just one person (e.g., service users, community member, etc.)	The original model accounted for the number of people (i.e., those deemed material) who experienced the outcomes, based on available documentation. When we accounted for only a single person experiencing each outcome, the ratio was 0.35
Scenario 4: Increasing the quantity of service users affected by 25%, reflecting an estimated increase in service access since 2023	The original model accounted for outcomes occurring between May 2023 to April 2024. Since then, there have been reported increases in service access and the number of service users who need support [e.g., (71)]. Increasing the quantity of service user experiencing each outcome by a conservative estimate of 25% resulted in the model increasing from 4.44 to 8.69
Scenario 5: Increasing the quantity of service users affected by 100%, reflecting an estimated increase in service access since 2023	Increasing the quantity of service users experiencing each outcome by 100%, which more closely reflects reported estimates [e.g., (71)] resulted in the model increasing from 4.44 to 21.51
Scenario 6: Increasing the quantity of service users, reflecting the number of reported overdoses in early 2025	In March 2025 alone, there were nine deaths and over 435 overdoses reported (72). Increasing the quantity of service users who avoided overdoses or had an overdose reversed to 435 increased the original ratio from 4.44 to 79.49