Simpson's Paradox in Measuring Net Dollar Retention Rate
Net Dollar Retention is one of the most important metrics is a SaaS business. It measures the value of a cohort of customers over time including expansion, cross-sell, and churn (loss of revenue). But how do you measure NDR?
Imagine this is your company’s data. The first column is the cohort month for each cohort in a year. The second column is the revenue of this cohort in their first month. The second colum is a random number between -20 and +20 that is the NDR for that cohort. The last column is the ending revenue of that cohort.

We are 12 years into the longest bull market in US history and this bullishness has powered the venture market. Investors deployed $117 billion in 2019 up from $106 billion in 2018.. This market has grown 20% over the last five years. It’s been go, go, go for nearly a decade.