business index vs index number

business index and index number both are nouns.

Word	Noun	Adjective	Verb	Adverb
business index	Yes	No	No	No
index number	Yes	No	No	No

As nouns, index number is a hypernym of business index; that is, index number is a word with a broader meaning than business index:

business index: a statistical compilation that provides a context for economic or financial conditions
index number: a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time

Other hypernyms of business index include index, indicant, indicator.

business index (noun)	index number (noun)
a statistical compilation that provides a context for economic or financial conditions	a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time