Human progress happens at 4% per year

I had to blog this with a headline like that!

Progress in Usability: Fast or Slow?
Jakob Nielsen's Alertbox
February 22, 2010:

...

Stephen Moore and Julian L. Simon wrote a book called It's Getting Better All the Time that summarizes improvements in 100 different fields across the 20th century. Following are some of their statistics (all from the United States):

• Infant mortality: 100 per 1,000 births in 1915, dropping to 9 in 1998. Improvement rate: 3% per year.
• Children without dental cavities: 26% in 1971, increasing to 55% in 1988.
  Improvement rate: 5% per year.
• People showering or bathing daily during winter: 29% in 1950, increasing to 75% in 1999. Improvement rate: 2% per year.
• Time worked to buy a chicken (at an average worker's salary): 2 hours in 1920, dropping to 15 minutes in 1999. Improvement rate: 3% per year.
• S&P stock market index: 6 in 1900, growing to 1,400 by 1999. Improvement rate: 6% per year. (As it turns out, 1999 was a bubble year, and the S&P later dropped, but for the sake of the long-term analysis, I'm sticking with the book's 20th century data.)
• Toy sales: $2 billion in 1921 (adjusted to 1998 dollars), growing to $45 billion in 1998. Improvement rate: 4% per year.
• Farm productivity, sacks of onions per acre: 200 in 1950, increasing to 800 in 1999. Improvement rate: 3% per year.
• Deaths caused by Chicago heat waves: 10,000 in 1901, dropping to 300 in 1995. Improvement rate: 4% per year.
• Airplane speed: 37 miles per hour in 1905 (Wright brothers Flyer III), increasing to 2,070 miles per hour in 1965 (Lockheed YF-12A). Improvement rate: 7% per year.
  

I could go on (the book has 100 datasets), but the conclusion is clear: Human progress happens at 4% per year, averaged across many fields, ranging from 2% to 7%.