It took 200,000 years for humans to reach 3 billion in number. It took 40 years for the next 3 billion.
11
Awarding people money for doing well in IQ tests causes them to score better, $10 increased people's score by an average of more than 20 IQ points. IQ tests don’t just measure intelligence - they also measure effort.
9
Forty percent of Americans have never visited a dentist.
33
Only 2% of the Earth's population are natural redheads.
13
Dutch, on average are the tallest people.
187
People with blue eyes are better able to see in the dark.
153