I'm interested in knowing what portion of Internet connected workstations are directly connected to the Internet (that is, the workstation has a dedicated Internet-routable IP), compared to those that are connected via a firewall or NAT device.
My guess is that the vast majority are NAT'ed?
My Grand Internet Control Panel shows that, at the moment, 71.82% of Internet-connected hosts are behind NAT.
I would assume that a very high percentage are NAT'ed. I know this wasn't always the case. When I started working for Earthlink, Inc all the workstations had public IPs. We have 4-5 full Class C networks only for the workstations on the LAN.
I worked at a major Canadian University for a while. All it's IP addresses were public. They had a class B, if I recall. That said, most workstations are probably NAT'ed, at least when there are multiple devices in the home. Most ISP's still give a public to each residential and business customer - though I do wonder how long that practice will last.
No direct answer to your question, I'm afraid - though I know there have been studies done.
Finding a solid number may be hard, often it just depends on the address spacing available at the time. I attend a popular college in Ontario, Canada that has their own class B-- I'm not sure what the reasoning was at the time of design but currently all of the IP phones and network printers have public addresses (whether they're accessible from WAN is another topic).
