While the population of the Earth as a whole continues to grow, many countries are experiencing a decline in birth rates, and they're concerned. Because older generations rely on younger generations (or the "working generation") for support, a stable population is essential. Encouraging procreation isn't easy though, so these countries had no other choice but to get creative.
Despite being the happiest country in the world, according to the World's Happiness Report from the United Nations, Denmark has a problem, and it has to do with sex. And babies. At 10 babies born per 1,000 residents, Denmark's birth rate was at an all-time low in 2013. A travel company decided something needed to be done, so it started a campaign called "Do It for Denmark!" The travel company is concerned about supporting an older population so encouraged Danes to travel, a time when they're arguably more likely to have sex.
It didn't hurt the company's business either, so it's a win-win.