Table 2.

Double-bounded dichotomous choice model estimates of willingness-to-accept conditional incentives (USD$) for prevention of HIV & other STIs among MSM in Mexico City

	Point estimate (USD$)	95% Confidence interval (USD$)		N	Covariates
Monthly model: prevention talks and STI testing
All MSM participants	9.5	9.1	9.9	1,573	No
All MSM participants	9.3	7.3	11.6	1,120	Yes
Male sex workers	6.8	5.9	7.8	75	No
Male sex workers	7.4	2.5	20.2	64	Yes
MSW or sex partners/month >=5	8.1	7.3	8.9	214	No
MSW or sex partners/month >=5	8.0	6.2	9.7	180	Yes
Quarterly Model: staying free of STIs verified by STI testing
All MSM participants	46.0	42.9	49.0	1,599	No
All MSM participants	44.0	37.5	50.7	1,130	Yes
Male sex workers	18.4	15.0	21.8	76	No
Male sex workers	15.0	–	45.8	64	Yes
MSW or sex partners/month >=5	29.0	24.6	33.3	215	No
MSW or sex partners/month >=5	29.8	18.7	41.1	178	Yes
Implied combination yearly model: prevention talks, staying free of STIs, and STI testing
All MSM participants	297.8	281.2	314.4	1,573	No
All MSM participants	287.9	238.4	342.4	1,120	Yes
Male sex workers	155.5	130.6	180.3	75	No
Male sex workers	148.3	30.6	426.3	64	Yes
MSW or sex partners/month >=5	213.0	186.5	239.6	214	No
MSW or sex partners/month >=5	215.1	149.1	280.4	178	Yes

Notes: MSM= men who have sex with men; MSW=male sex worker

Amounts expressed in USD$ of October-December 2008 using average exchange rate of 12.97 pesos per $1 USD.

Table presents results from double-bounded dichotomous choice model estimated in Stata 11 MP, 64 bit.

Models estimated by maximum likelihood based with a modified “doubleb” Stata ado file for willingness to pay [50].

Monthly model data refers to random incentive offer α1 and bargaining incentive offer α2 to attend HIV/STI prevention talks and STI testing.

Quarterly model data refers to random incentive offer α3 and bargaining incentive offer α4 to stay free of STIs, verified by quarterly STI testing.