Definitions for "Index number"
An index number is a statistic indicating the relative change occurring in the price or value of a commodity, share price or in a general economic variable e.g. retail price increases, with reference to a previous base period conventionally given the number 100.
A numerical , usually indicating, by comparison with a base value of 100, the size of the index relative to a base year or other benchmark for comparison. Thus, for example, a CPI of 115 in 2004 with a base year of 1999 means that the index has risen 15% from 1999 to 2004.
a weighted average of a number of statistical observations of some economic attribute, as a percentage of a similar weighted average calculated for the attribute at an earlier, or base, period; typical economic attributes for which index numbers are calculated are prices and production, the most familiar being the cost-of-living index. weighted average meteorology
Keywords:  tulips, bread, average, weight, goods
an average in which some goods (bread) are given relatively more weight than other goods (tulips)