About 1 in 3 people own a brokerage/investment account. This may be in a form where they do not even realize they are trading (Like passive mutual funds or ETFs).
Also, about 1 in 3 people use internet banking or some form of online financial services.
Although it is not so sophisticated, we could argue 1/9 people care to have some online brokerage activities.
For sanity check: Scotttrade, Fidelity, Schwab, TD Amitrade are the larger online brokerages, their estimated brokerage customer base is ~40m. So we are not way off with 1/9. Also because some countries have less internet adoption.
One interesting e-broker is etoro.com
Why? They have over the counter derivatives for ETH and BTC. The buyers do not have any idea how ETH or BTC works. They do not have addressess or private or public keys. They just believe etoro that they own ETH or BTC. This easy.
Also, etoro has nice statistics on its user base and traded products. here you can see, they have 1.8m people following BTC. and 46% is investing in it! There you go, 800,000 people that invest in BTC. Small or big, does not matter. A lot of people exposed to it. Another 200,000 people invest in ETH (guessing 95% overlap).
Etoro is a mid-sized brokarage, with about 6m customers. But by no means are they irrelevant. Major account holders exist and it is known as innovative. So, we can say they represent the early adaptors of the mainstream. No geeks on there, just investors with some higher risk appetite/interest in figuring out what's next.
This is in my opinion the first wave of adopters proven. Either more people will jump on such solutions or classical ebrokers will offer OTC crypto funds. We will see.
One thing is clear: We are no longer 0,01%!!! At least a million BTC address holders exist, and another 2 million at cryptoexchanges, another million on etoro already. So think of ~ 5m people already owning digital assets! Imagine the world has 1bln people with some sort of money to invest; we are 0,5%!! And the way is up. But it will be a bumpy ride :)