# Age at first intercourse

This indicator is a summary measure of the average age at which adolescents become sexually active. Evalua­tors may alternatively calculate the indicator as: (1) the mean age at first intercourse, (2) the median age at first intercourse, or (3) the percent of youth who have ever had intercourse by selected reference ages (e.g., age 13, 15, 17, 19).

1. Mean age at first intercourse

2. Median age of first intercourse1

MEDIAN= L+[(50-cf/f)*i]

Where:

L = the true lower limit of the class interval in which the median is located; 50 = the 50 percentile observation; cf = the cumulated frequency up to the median class interval;

f = the frequency within the median class interval; and

i = the class width.

1 Note: This formula is for use with grouped data consisting of percentage frequencies in each class. For ungrouped data, the median is the value of the observation falling at exactly the 50th percentile of the distribution of observations

3. Percent of youth who have had intercourse at refer­ence ages

 # of adolescents of a reference age who report having had intercourse x 100_________________________________________________________Total # of adolescents of the reference age

Self-report by adolescents on whether they have ever had intercourse and, if so, their age at first intercourse. Obtaining current age is also useful for more refined measures (see below). Evaluators should measure the indicator for both married and unmarried youth.

Surveys of program participants or adolescents in the program‘s intended population

The typical or average age at which adolescents in the program‘s intended population are initiating sex is an important parameter for program design purposes and a key outcome indicator for programs aimed at delay­ing onset of sexual activity.  The preferred form of the indicator is the median age at first intercourse, as this form avoids bias problems that arise in the use of the mean age in settings where sexual initiation typically occurs at later ages. If fewer than 50 percent of the sample is sexually active, the preferred form of the in­dicator is the proportion of adolescents who had initi­ated sex by specified reference ages among respondents who are the reference age or older (e.g., the percentage of adolescents 16 years of age or older who had initi­ated sex by age 15). Evaluators may compute median ages at first pregnancy or birth in a similar fashion.

sexually transmitted infection (STI), family planning, HIV/AIDS, adolescent, behavior

Whereas menstruation is considered a sign of a young girl‘s passage into womanhood, in many societies, first sex marks a young man‘s initiation into manhood. Boys generally initiate sex earlier than girls, because many cultures tolerate or encourage sexual activity among adolescent males. In some places, a young man‘s masculinity is questioned if he has not had sexual intercourse by a certain age (McCauley and Salter, 1995).  Re­sponses to the question of age at first intercourse may thus be misreported because of cultural norms that may encourage boys to boast about early sexual experimentation, while having the opposite effect on girls, who may underreport sexual activity because of the great value placed on vir­ginity.

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