Household income seemed to correlate positively with WTP

In a study  on the value of Koren Public Libraries, participants were asked how much they would be wililng to pay for library services:

Household income aslo seemed to correlate positively with WTP [wilingness to pay] responses. That is, the higher the household income was, the higher the WTP bid.

Geographic Region: 
Age Group: 
Type of Library: 
Category: