Estimating sexual behavior parameters from routine sexual behavior data

In mathematical models for predicting the spread of sexually transmitted diseases (STDs), the rate of acquisition of new sex partners and concurrency, the number of simultaneous sexual partnerships, are important parameters. Yet, information on these parameters is rarely obtained in routine sexual behavior surveys; instead, questions about the total number of sex partners during specific periods are often asked. We present two methods that estimate the rate of partnership acquisition and concurrency from reported numbers of sex partners in two overlapping periods. The first method assumes homogeneous behavior, while the second method also takes account of heterogeneity in sexual behavior. Both methods assume random (Poisson) partnership acquisition and the possibility of overlap in relationships. For both methods it might be relevant to distinguish individuals who are in a stable relationship from those who are not.