A method and system for determining investor participation driven stock purchase indices. Raw customer trading data is received from an accounting system. The raw customer trading data is then aggregated to generate daily transaction total counts for all stocks (that is, total shares bought and sold, total market value, etc.) as well as daily transaction total counts for each individual stock. Aggregation of the raw customer data also addresses customer privacy concerns. The aggregated data is processed to produce moving averages, stock purchase indices, and stock rankings. The stock purchase indices are based on a diffusion index technique of segregating buyers from sellers, and with these relative counts, measures the breadth of investor purchasing participation. The stock purchase indices are then displayed to a graphical user interface. The display includes stock buy and sell ranking lists.