The Canadian Community Health Survey is an annual voluntary survey, carried out by Statistics Canada, that collects information about a wide range of health outcomes and risk factors. As part of the 2013-14 survey, 47,764 Canadians between the ages of 15 and 49 were asked about their sexual activity - whether or not they have ever had sex, and if they have had sex in the past year.
The majority of those surveyed reported being sexually active, as shown in the graph below. For example, about 88 percent of 18-19 year old women surveyed in 2013-14 (or 0.88) reported having sex in the last year. For women, the probability of having had sex in the past year peaks at age 25-29. For men, it peaks 10 years later at ages 35-39.
These estimates, because they are based on survey data, are subject to some margin of error. The vertical bars represent 95 percent confidence intervals - the true population mean will lie within that confidence interval 19 times out of 20. When there is little to no overlap between two confidence intervals, it is fairly certain that one group of people is having more sex than another group of people. So it is possible to say, with a high degree of confidence, that 18-19 year old girls are more likely to be sexually active than 18-19 year old boys, and 45-49 year old men are more likely to be sexually active than 45-49 year old women.