prevalence

(noun) the quality of prevailing generally; being widespread. Example: "He was surprised by the prevalence of optimism about the future."

(noun) (epidemiology) the ratio (for a given time period) of the number of occurrences of a disease or event to the number of units at risk in the population.

(noun) a superiority in numbers or amount. Synonyms: preponderance. Example: "A preponderance of evidence against the defendant."