Forget Happy. Satisfaction is the key metric here.
Customer satisfaction is so hard to achieve because it changes from customer to customer and day to day. It is ever moving.
However, you can tell if a customer is satisfied by looking at the following three criteria:
1. How much do they conistently buy from you? Is the rate increasing or decreasing? Satisfied customers find a way to do more business with you.
2. Do they pay their bills on time? Satisfied customers pay on time.
3. Do they give you referrals? If asked, satisfied customers give referrals.
How do you measure satisfied customers?