Tracking Retail Money

Robinhood is the popular (read free) though glitchy trading app.
Robintrack is a service that tracks the number of Robinhood users that hold a particular stock over time against the share price.
Pictured below are the shares of Carnival Cruises, which have collapsed due to coronavirus. Yet retail investors have been buying.
Something similar but less informative exists for the UK – Top of the Stocks at Hargreaves Lansdown.