Acquisition Retention Spending Ratio provides companies with an insight into the amount they spend to acquire new customers compared to the amount they spend to retain. In most industries it is significantly more expensive to acquire new customers.
Acquisition Retention Spending Ratio = Spending to acquire new customers / spending to retain existing customers
This indicator will be included in my book: Key Performance Indicators - the 100 measures every manager needs to know, which contains an in-depth description of this KPI, as well as practical advice on data collection, calculations, target setting, and actual usage.