"By signing up as a new user once a week and observing your own user id you can measure the rate of growth of a competitor." I've done similar with cheques. In

"By signing up as a new user once a week and observing your own user id you can measure the rate of growth of a competitor." I've done similar with cheques. In a previous job, I was paid by cheque. Each month, I logged the cheque number. From this and taking into account other payment methods, I determined that the company had significantly fewer transactions than the boss claimed.