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9.1.3 Sex before the age of 18.
Program Area: Young people's sexual behavior 
Definition: Percentage of young people 20-24 who have had sex before the age of 18.  
Numerator: Young people 20-24 who report their age at first sex as under 18.  
Denominator: All young people age 20-24. 
Measurement Tools: A nationally representative general population survey.  
What It Measures: This indicator provides information on the prevalence of early sexual initiation among young people.Sex at young ages is thought to be more risky than sex later in life. The female genital tract is more susceptible to infection with HIV before it has fully matured. Typically, young people have partnerships that are more often of short duration and perhaps less formal than those of older people. Moreover, they are less likely to live with their sexual partners, and this can often result in one of the partners having additional concurrent partners, increasing the risk of infection. People who begin having sex at young ages may spend a longer time in such less stable sexual relationships than people who delay their first sexual intercourse. Moreover, they may be more likely than older people to be bullied or exploited in sexual relationships. 
How to Measure It: This indicator is derived from answers to a question about the age of the respondents when they first had penetrative sex, either vaginal or anal. Typically, this question follows one on whether the respondents have ever had sex. The indicator should be presented as separate percentages for males and females, and should be disaggregated by the age groups 15–19 and 20–24 years. It is difficult to monitor change in this indicator over a short period because only individuals entering the group, i.e. those aged under 15 at the beginning of the period for which the trends are to be assessed, can influence the numerator.  
Strengths and Limitations: The advantage of using the reported age at sexual initiation is that it makes the most use of data that are already collected. Previously, sexual initiation has been measured by calculating the median age at first sex. Three different methods of calculating this value were proposed, each of which had unique limitations and produced different results. The above calculation is simple and allows easy comparison between times. The denominator is easily defined because all members of the survey sample contribute to this measure. For most people, first sex is a significant event that they probably remember with little difficulty. People may, however, be unsure of their exact age. The responses of young people of both sexes may be influenced by views on young people’s sexuality in the society in which they live. An analysis of the reporting of age at first sex, however, has shown that the occurrence, extent and direction of reporting or recall bias are not predictable.  
Use of Indicator:  
Tools:  
SSO Code:  
UNGASS: Yes 
The President's
Emergency Plan:
No 
OVC: No 
MDG: No 

USAID | UNAIDS | UNICEF | WHO | CDC | US Census Bureau
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