Short answers, pulled from the story.
Numeracy is the ability to understand, reason with, and apply simple numerical concepts; it is the numerical counterpart of literacy. The National Numeracy charity defines it as understanding how mathematics is used in the real world and being able to apply it to make the best possible decisions, emphasizing that it involves thinking and reasoning as much as performing calculations.
The term innumeracy was coined by cognitive scientist Douglas Hofstadter. It was later popularized in 1989 by mathematician John Allen Paulos in his book Innumeracy: Mathematical Illiteracy and its Consequences.
Children under the age of five have the best opportunity to absorb basic numeracy skills. Research comparing five-year-olds and seven-year-olds found that the differences in knowledge retained were greater among the younger group, indicating that earlier ages offer a higher capacity for learning numeracy.
Innumeracy can lead patients to overestimate their chances of survival or choose lower-quality hospitals. It can make medical graphs impossible to read correctly, and misunderstandings between doctors and patients about numerical health information can result in serious harm.
Children from Singapore had the highest performance at both the fourth-grade and eighth-grade levels in the 2003 Trends in International Mathematics and Science Study. Hong Kong SAR, Japan, and Taiwan also ranked among the highest-performing countries.
Psychometric numerical reasoning tests became prevalent during the 1980s, following pioneering work by psychologists including P. Kline, who published A handbook of test construction: Introduction to psychometric design in 1986. These tests are administered by occupational psychologists to assess job applicants' ability to comprehend and apply numbers.