The issue IMO is not overpopulation or underpopulation. All around the world, people with high IQ are being replaced with people with lower IQ. Population growth is taking place in regions such as Sub-Saharan Africa and the Middle-East, where the people are illiterate and unskilled. On the other hand, maximum population decline is being noted in regions such as East Asia (Japan, Taiwan, South Korea.etc), where there is 100% literacy. In the long term, this brings down the levels of human innovation.
As awful as it may sound, you're right. Western countries are facing underpopulation, due to the financial crisis and the deteriorating situation, the west isn't having children. Third world developing countries, however, in Asia (see Indonesia, India) or Africa, are extremely overpopulated, often living in terrible living conditions, with poor hygiene and housing, lacking access to water and food.