New census data on age and sex show that as of May 15, 2001, the median age of Canada's population reached an all-time high of 37.6 years, an increase of 2.3 years from 35.3 in 1996. This was the biggest census-to-census increase in a century. Median age is the point where exactly one-half of the population is older, and the other half is younger. The nation's median age has been rising steadily since the end of the baby boom in 1966, when it was only 25.4 years. Nova Scotia and Quebec were the nation's oldest provinces, each with a median age of 38.8 years. Alberta was the youngest with a median age of 35.0. The group to increase at the fastest pace was that aged 80 and over. From 1991 to 2001, their numbers soared 41.2% to 932,000. The number of people aged 80 or over is expected to increase an additional 43% from 2001 to 2011, during which time it will surpass an estimated 1.3 million. At the same time, Canada has undergone a substantial decline in the number of children aged four and under. In 2001, the census counted 1.7 million children in this age group, down 11.0% from 1991, the result mostly of Canada's declining fertility rate. By 2011, this group may decline to an estimated 1.6 million.