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How to Lie with Statistics

Quick Math Checks

Can you quickly evaluate whether or not a reported statistic seems reasonable?
[Sources deliberately not cited for the following statistics; verify them yourself rather than trusting this page blindly.]

World Population

  • 6 billion -- it is actually estimated as 7.5 billion in 2017, but 6 is easier than 7.5 to use for quick math estimates
  • 1 billion in China (2017 estimate = 1.4 billion)
  • 1 billion in India (2017 estimate = 1.3 billion)
  • 500 million in European Union (2016 estimate = 508 million)

U.S. Population -- if something happens to almost every American once in their lifetime, how many each year?

  • Adjust the actual values to simplify the math (2017 U.S. population = 326 million; 2017 U.S. life expectancy = 76.73 years)
  • Divide 300 million Americans by life expectancy of 75 years = 4 million Americans per year
    • 4 million Americans are born each year
    • 4 million Americans die each year
    • 4 million Americans turn 21 each year
  • 4 million Americans per year equivalents:
    • 300,000 Americans per month (333,333)
    • 75,000 Americans per week (76,923)
    • 10,000 Americans per day (10,958)

Average individual's time spent at work in a year

  • 50 weeks = 52 weeks - 2 weeks (vacation, holidays)
  • 250 days = 50 weeks x 5 workdays/week
  • 2,000 hours = 250 days x 8 hours/day

Power of 2 -- how quickly does doubling grow?

  • 2^2 = 4
  • 2^5 = 32
  • 2^10 = 1,024 or approximately one thousand
  • 2^20 = 1,048,576 or approximately one million
  • 2^30 = 1,073,741,824 or approximately one billion

Rule of 72 -- approximately how many years are required to double something at a given annual percentage growth?

  • Divide 72 by the percentage
  • 72 / 2% = 36 years
  • 72 / 3% = 24 years
  • 72 / 4% = 18 years
  • 72 / 6% = 12 years
  • 72 / 8% = 9 years
  • 72 / 9% = 8 years
  • 72 / 12% = 6 years