Buying Rate

Buying Rate is a panel data measure.  It is the average amount of product purchased by one buying household over a whole time period (usually a year).  It can be expressed in dollars, units or EQ volume.  In Nielsen the fact is called Item Sales per Item Buyer.  In IRI the fact is Sales per Buyer.

If annual buying rate for Brand X is $15.53, it means that each household who bought Brand X spent, on average, a total of $15.53 on it over the course of the year.

Sales = (Total # of Households x Penetration) x Buying Rate

Buying Rate = Purchase Frequency x Purchase Size

Reference articles: Panel Data Dictionary, The Panel Chart Every CPG Analyst Should Understand.