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Human Numbers 

• 0.1% - 0.2% - Live births with gender ambiguous enough to become the subject of specialist medical attention, such as surgery to disguise their sexual ambiguity (WP)
• 0.3 - Avg IQ points gained each year since 1947 (WISC, WAIS, Stanford-Binet) (WII p112)
• 1 - IQ points per generation lost due to U.S. reproductive patterns (WII p101)
• 1% - Human live births with some degree of sexual ambiguity (WP)
• 10 - There are 10 times more bacterial cells than human cells in the human body (WP)
• 15-30% - Rate at which people are wrong about things they consider 98% certain (Black Swan)
• 16% - Percent of the variance in IQ accounted for by variation in brain volume (Scientific American Mind, Aug/Sep 2008 p63)
• <=20 seconds - Short term memories
• 17.5 - Avg times people laugh per day (Rod Martin, University of Western Ontario, \"The Psychology of Humor\" 
• 51% - Chance that a typical coin flip will result in the side that was facing up before the flip (see coin flips are not 50-50 )
• 70% - Approximate portion of U.S. food that is genetically modified
• 25,000 years ago - Homo Sapiens had become only living species in hominin genus with exception of Homo floresiensis ("Hobbits")
• 100,000 years ago - First traces of unambiguous use of symbols (NYRB 10/22/09)
• 200,000 years ago - Single female ancestor of all humankind, Homo Sapiens appear
• 500,000 years ago - human brain size had reached current capacities (NYRB 10/22/09)
• 5-7 million years ago - Common ancestor of humans and chimpanzees (from DNA, not fossils, NYRB 10/22/09)
• 10 million - Odds that your vote will affect the presidential election = 1/10,000,000 (FiveThirtyEight.com)
• 10^600 - Odds of a mother conceiving a child genetically identical to another (but not an identical twin) (Source)

Nature Numbers

• 186,283 miles/second - Speed of light (c) = 3x10^10 cm/second
• 1 million - Bacteria in approx. mililiter of fresh water
• 5 nonillion (5x10^30) - Approx. bacteria in the world
• 3.5 billion - Years, Oldest known fossils
• 4.28 billion - Years old, oldest rock known (Canada) ("Science" SGU #167)
• 426 billion - Trees on earth (approx 61 trees/person) - [Krulwich 11/12/08]

• 10^18 cm = 1 light year
• 10^-8 cm - Angstrom (=~ diameter of atom)
• 1836x - Mass of proton to mass of electron
• 6.022 x 10^23 atoms/mole - Avogadro's number
• 5 million years - Common ancestor to chimpanzees and humans (CUK p.86)
• 10^80 - Atoms in the known universe (Source)
• Gavitational/weight changes on humans (SI 18.5 p513)
  • 0.000035% - change in weight from moon overhead to on the horizon
  • 0.3% =~ change in weight due to changes in weather
  • 0.5% =~ change from moving from place to place on earth's surface
  • 1% =~ weight change from meal

Traffic Numbers

• .5 mile = as far as most people will walk for things like groceries - p138
• 30 seconds - Tipping point for jaywalking and accepting smaller gaps to turn against traffic - p225
• 3 seconds - In 80% of crashes and 65% near crashes, driver was not paying attention to traffice for 3+ seconds before event (trouble starts at 2 seconds)
• 0% - Effect that anti-lock brakes have on reducing crashes (never explained) - p263
• 5% - Crashes that involve two vehicles moving in the same direction - p253
• 50% - auto accidents are at intersections - p178
• 85% - People killed in work zones that are drivers or passengers, not workers - p45
• 90% - Fewer fatalities at roundabouts than intersections with stop signs (76% fewer injuries, 40% fewer crashes) - p179
• >50% - Traffic fatalities that are single vehicle, run off road - p185
• 2x - Chances that striking pedestrians at 36-45 mph will kill them compared to 31-35 mph - p206
• 4x - Chances that striking pedestrians at 36-45 mph will kill them compared to 26-30 mph - p206
• 2.5x - Death rate on rural, non-interstate roads compared to all other roads - p257
• 7x - Chances that person drinking within legal limits will be in a fatal crash - p251
• 10x - Chances that people with personality disorder will get in a serious crash - p261
• 15x - Chances that people in cars going 50mph will die relative to cars going 25mph - p252
• 13x - Chances that legally drunk person will be in fatal crash - p251
• 22x - Chances of motorcycle ride resulting in death relative to average car
• 1.3/100 million miles - Traffic fatalities of male drivers
• .73/100 million miles - Traffic fatalities of female drivers
• 1/100 - Chances that average drive (15,500 miles/year) will die in 30 years of driving - p249
• 10,000 - Estimated lives could have been saved if U.S. did what U.K. did in the 90s. - p271