Growth Rate/trend identification

Hi All,

I need your help in calculating growth rate/trend

I do not want to use the existing definition of growth rate.

An example is below of a customer spending details per week

1 10
2 20
3 45
4 55
6 20
7 0
8 0
9 5

I need to know whether the customer in increasing his spend or not and by how much is average week on week growth rate.

I need to do this for a list of customers.