The percentage of customers that have placed n order that also placed n-1 orders.
Formula
nth Order Rate = Unique Customers with n Gross Orders / Unique Customers with n-1 Gross Orders
Explanation
This KPIs can be used to calculated for example what percentage of customers that have placed a third order also have placed a fourth order.
In this case n=3 and thus the KPI would be called Third Order Rate.
But n can be any positive number.
Notes
The 2nd Order Rate is the same as the New Customer Repurchase Rate and while it can be used like this, we will always use the terminology New Customer Repurchase Rate in this scenario.
The nth Order Rate is used when looking at Repeat Customer behaviour. The complete repurchase rate of repeat customers is called Repeat Customer Repurchase Rate. The nth Order Rate is used to look at subsets of this KPI