The data

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Data from the 2003 and 2009/2010 Canadian Community Health Survey (CCHS) were used to estimate the prevalence of sexual activity, the number of sexual partners, and condom use among 15- to 24-year-olds. Data for the 2003 CCHS were collected from January through December. In 2007, the survey changed to continuous collection; the data for 2009/2010 were collected from January 2009 through December 2010. The response rate for 2003 was 81%, and for 2009/2010, 72%. Most interviews—70% in 2003 and 62% in 2009/2010—were by telephone. The samples used for the analyses in this article numbered 18,084 and 15,966 respondents aged 15 to 24, weighted to represent populations of approximately 4.2 million in 2003 and 4.4 million in 2009/2010. Details about the survey design and sampling techniques have been published elsewhere.¹²

All differences were tested to ensure statistical significance at the 0.05 level. To account for survey design effects, standard errors and coefficients of variation were estimated using the bootstrap technique.¹³

The percentage of 15- to 24-year-olds who had had sexual intercourse at least once was based on "yes/no" responses to the question, " Have you ever had sexual intercourse?"

Estimates of the percentages of 15- to 24-year-olds who became sexually active before age 15 or at ages 15 or 16 were calculated from responses to the question: "How old were you the first time?"

Respondents who reported ever having had sexual intercourse were asked, "In the past 12 months, have you had sexual intercourse?" Those who replied affirmatively were asked, "With how many different partners?"

Condom use was calculated among sexually active 15- to 24-year-olds who had been with multiple partners in the previous 12 months and/or who were not married or in a common-law relationship. The estimates were based on responses to: "Did you use a condom the last time you had intercourse?" Because condom use pertained to the most recent sexual encounter, it may not reflect typical behaviour.  However, reports of condom use at the last sexual contact have been shown to approximate usual behaviour.¹⁴

The data about sexual behaviour in this article are self-reported, and so are subject to social desirability and recall biases. Social desirability is the tendency to modify answers to present a more favourable image. The impact of this phenomenon on estimates of sexual behaviour is difficult to quantify because the perception of what is "desirable'' may differ depending on the respondent's age, sex and socio-economic status. Some individuals may give socially acceptable answers (under-report) to questions about sexual behaviour; others may exaggerate their sexual experience. Establishing the veracity of reported sexual activity remains a challenge, as no universally accepted means of validation exists.¹⁵ However, studies that have used test-retest reliability methodology to verify self-reported sexual activity,^16,17 condom use,¹⁸ and age of first sex¹⁷ find that adolescent reports are generally reliable. Moreover, the CCHS questions were developed through expert consultations and tested extensively to help ensure data accuracy and relevance.¹⁹

Because the CCHS is a household survey, the results can be generalized to the Canadian household population. This is an advantage over school-based surveys, which are often used to collect data about the sexual behaviour of young people, but which exclude youth no longer in school, a population that could be at high risk of contracting sexually transmitted infections and the Human Immunodeficiency Virus (STI/HIV). 

Some information that would help to better understand the sexual habits of youth are not available on the CCHS, including relationship status and sexual partner characteristics. As well, the term "sexual intercourse" was not defined in the CCHS, so it is possible that some respondents may have misinterpreted the question.²