the real Marketcap?

[eddy1337]

I have been thinking, and a lot of people only use Bitcoin to transfer funds from location to location and then change it to Fiat again.. This happens thousands of times each day at millions of dollars each day as well..

So how can we know the real marketcap when people withdraw fiat money all the time from Bitcoin, (examples are Bitpay and so on that pay merchants every day to their bank account)

So how much bigger than 20billion is really the market? 100? 1000? Will we ever know?