It was assumed that:
(1) without intervention, no changes would occur in risky behaviours in the target population over time;
(2) less risky behaviour due to the intervention would last for only 1 year before relapsing to the previous level of risk;
(3) the selection of partners would occur without consideration to their HIV serostatus;
(4) the age distribution in the target population was equal;
(5) a zero growth rate was assumed for the target population during the 10-year period.