To create a segment of customers based on spending behavior, what building block should be used?

To create a segment of customers specifically based on spending behavior, utilizing an aggregate of transaction events is the most appropriate building block. This method focuses on the collected data from various transactions, which allows for a comprehensive understanding of how much customers are spending over a defined period. By analyzing these aggregate transaction events, marketers and analysts can discern patterns in customer behavior, such as total spent, frequency of purchases, and the average transaction value, all of which are vital to understanding spending habits.

The other options, while valuable in their contexts, do not directly correlate with spending behavior. A composite of individual purchases provides details on single transactions without offering a holistic view. Customer demographic attributes might assist in targeting segments but do not reflect spending behavior directly. Recent website activity may indicate interest but lacks the direct connection to actual purchase behaviors or spending patterns. Thus, focusing on transaction events ensures that the segmentation is based on real expenditure data, making it the most effective choice for analyzing and leveraging customer spending behavior.