Once there were just two nuclear powers — the United States and the Soviet Union. Now there are at least nine. But despite the increase in the number of states with nuclear weapons, there has been a dramatic decrease in the number of such weapons since the end of the Cold War. We wonder: How many nuclear weapons are left?
Global consumption of cigarettes has risen steadily since manufactured cigarettes were introduced at the beginning of the 20th century. While consumption is leveling off and even decreasing in some countries, worldwide more people are smoking. We wonder: How many smokers are there worldwide?
One of the best ways to measure improvements in the global environment is to look at the level of greenhouse gas (GHG) emissions — which are widely believed to contribute to global warming — in relation to the size of a country’s economy. We wonder: Which of the following countries is closest to the level of the United States in this measure of emissions intensity?
Living in cities is more popular today than it has ever been — and cities are growing in size. In fact, nearly half of the world’s population alread lives in urban areas. So we wonder: How many countries in all of Europe have populations that are smaller than that of Greater Paris, with its 9.8 million people?