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Innumeracy is a term used to the inability of people to understand numbers, statistics, and probabilities. The first use of "numeracy" as an analogue to literacy was in a 1959 report by Geoffrey Baron Crowther and the derivation "innumeracy" was coined by Douglas Hofstadter and popularized by the book of the same title by John Allen Paulos. Numbers and probabilities are often essential to understanding the world, and ignorance, or even an anti-intellectual stance against understanding how they work, can lead to significant consequences personally and for society as a whole. The potential problems caused by innumeracy are, it must be said, innumerable.
What is numeracy?
Numeracy is generally defined as an understanding of, and ability to do basic manipulations with numbers: addition, subtraction, multiplication, division, fractions, percents, and decimals. When looking at basic innumeracy, it does not include algebra, geometry or calculus. The point is pretty simple: our kids, and in fact most of the adults in studies done in the US and UK, are unable to easily figure out the cost per item or how much they are saving if something is "25%" off.[better source needed]
Do numbers matter?
One criticism often brought up is the question of just how important skills like numbers and spelling are, in a world of calculators and spell check. After all, most people no longer know how to build a good fire, bake from scratch, or even sew on a button. Everyone carries a calculator with them, in the form of their phone; their browsers check the spelling as they type, and if they really need something, they can find a way to get the information. 
- Working numbers trains a mind for logical, critical thinking. The fact is, math, even basic numeracy, is a logically derived system. Learning to manipulate basic numbers gives you an entry into the thought processes that critical thinking are built upon.
- Basic numeracy allows people to make everyday comparisons. "Is this can of tuna that is 2 times the size of that can of tuna, a better deal, even though it is more expensive?" "Did turning off the lights really affect my utility bill?"
- Numeracy helps in understanding statistics, and therefore being able to understand how to better take risks, or who is selling you a load of bull.
- Numeracy helps you understand major life decisions like when to buy a house, and how to buy a house. If more people had better numeracy skills, they might not have been as willing to buy houses they could not afford, or waive payments off for 5 years, only to be hit with rates that are significantly beyond their reach.
While it is true that you can figure out all of these things with a calculator, people don't really bother. If they had a basic working grasp of these numbers, they could easily calculate much of this in their heads to make better decisions. And without a basic understanding of the underlying mathematics, you can't even work it out with a calculator.
A simple test of numeracy
A baseball and a bat cost $1.10 together. The bat costs one dollar more than the ball. How much does the ball cost?[note 1]
In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake (assuming the cover is perfect), how long would it take for the patch to cover half of the lake?[note 2]
Kids and innumeracy these days
Old people that yell at clouds, books like Innumeracy, and an earlier revision of our page that has remained for years, with no sources, suggest that innumeracy rates have been rising or are high among our younger generations and trot it out as an excuse for our failing public education system (as stated in a Chicago Tribune review of the book). This is, however, not supported by two studies W. L. Nelson et al. found that numeracy rates among a national representative sample from the U.S. have been consistently improving each new generation while Rashid et al found that recent generations were associated with more substantial gains in numeracy.
- The ball costs 5 cents and the bat is $1.05. Quick intuition would tell a lot of people that the bat is $1 and the ball is 10 cents, but that's only a 90 cents difference between the two, and if you factor the dollar difference, 10 cents plus $1.10 would be $1.20.
- It would take 47 days for the patch to cover the entire lake. After all, after day 47, the patch should double and then cover the lake. The "intuitive" (but incorrect) answer would be 24.
- John O'Donoghue. Numeracy and Mathematics. Irish Math. Soc. Bulletin 48 (2002), 47–55
- Douglas Hofstadter's Innumeracy Exercises, jsomers.net
- Innumeracy: Mathematical Illiteracy and Its Consequences
- Vann, John (1989-03-05). "Innumeracy". http://articles.chicagotribune.com/1989-03-05/business/8903240201_1_mathematics-innumeracy-trillion. Retrieved October 5, 2018..
- Nelson, W. L., Moser, R. P., & Han, P. K. J. (2013). Exploring Objective and Subjective Numeracy at a Population Level: Findings From the 2007 Health Information National Trends Survey (HINTS). Journal of Health Communication, 18(2), 192–205. doi:10.1080/10810730.2012.688450
- Rashid, Sammy; Brooks, Greg. University of Sheffield. "THE LEVELS OF ATTAINMENT IN LITERACY AND NUMERACY OF 13 - TO 19 - YEAR OLD IN ENGLAND, 1948–2009" National Research and Development Centre for adult literacy and numeracy; Institute of Education. London. Retrieved October 5, 2018.