I don't have data going back that far. My earliest data I have on-hand goes back to 1997 at which point about 2% of the world (11% in the developed world) had internet access. I do have host count data, though and can tell you that in August of 1983 there were a whopping 562 web sites in existence. In July 1997 when only 2 (or 11) percent of people had access, there were about 19.5 million. As of January of this year there are almost 900 million.

So let's extrapolate: There were about 5.84 billion people in the world in 1997, 2% of which is about 117 million people on the internet (round numbers). Thus, in 1997, we can estimate one in every 6 internet users had their own web site.

Today there are about 6.97 billion people in the world and about 35% of them have internet access (74% in the developed world, but I digress). This means that about 2.4 billion people are responsible for about 900 million web sites - that's one web site per 2.7 internet users. If we work backwards from this imaginary (and probably wrong) line, we can estimate that there were about 3,000 internet users back in 1983.

There are currently estimates that the Bitcoin network is made up of between 15 and 20 thousand users. Let's call it 15, just to be pessimistic. Adjusting for world population that puts us about on-par with the internet's adoption level in 1987. Bitcoun is about 4 years old, while the 1987 internet was about 6 years old, which means we're growing 50% faster than the internet did. Assuming nothing gigantic implodes along the way, Bitcoin is on its way to greatness.

Of course that's assuming you can compare Bitcoin to the internet, which you probably can't ;-)

As a fairly untechnical user, I would like to add that as soon as I figured out how to actually get bitcoins (bitinstant) the process became quite natural and the usefulness apparent.