In a project that I am doing to evaluate customer behaviour, I have asked a set of questions such as whether they read the unit pricing before they decide to purchase a particular product or do they only buy a particular product if it is on 'special'.

In a population of 60 stores (with unequal customer base but the total number of customers being 85,000), I used probability proportional to size (PPS) sampling method to constructed a sample of 1,000 customers. 

A total of 900 customers responded to the survey. The response rate is 90%.

Conversely, the non-response rate is 10%.

How 'acceptable' is this non-response rate? (I know the response rate for this example is impressive!)

What factors need to be considered when making a decision on whether this non-response rate is acceptable or not?