Humans are getting old. In 1800 your best bet was to live in Belgium which topped the life expectancy charts at 40 years. Average life expectancy grew from around 26 years in the Bronze Age to 48 years in 1955 and 67 years in 2010 and is expected to reach 73 years in 2025. There is of course a great inequality within the world. People live on average for just 32 years in Swaziland and 83 years in Japan.
At the same time, women are having fewer children. Some 2.3 children would have to be born per woman for global population growth to trend towards zero, but the ratio has dropped to below 1.5 in the most developed countries in recent years. As a result, the average age in these parts of the world is increasing and the population is getting older.
An average Czech was 41.7 years old in 2014 (with median exceeding 41 years), according to the Czech Statistical Office, compared to a figure of only 35 years in 1990. As we live longer (life expectancy of Czechs has increased from 73 in 1990 to nearly 78 now) and fewer children are born, the proportion of people aged over 65 might increase from 17% of the total population now to some 21% in 2030, according to the United Nations' estimates.
Czechs are one of the oldest nations in Central Europe, just behind Hungary, which already faces declining population growth prospects.
For detailed data for all countries since 1960, see Median Age