Solar has doubled every 2 years for 30 years

I read somewhere a while ago that solar capacity has doubled every two years for 30 years, but stupidly, I didn't keep the link, and I haven't been able to find it again.  But I stumbled across a different site which showed a slightly lower growth since 1975, namely 30% per year.  To double every 2 years the growth rate would have to be 41% per year.  So, in the early years, when solar was so expensive, obviously growth was lower, because we know that since 1990 it has doubled every 2 years.  Currently solar provides about 1.2% of global electricity, which means it is just 6 doublings (or 12 years) away from providing 80% of all electricity.

It's a nice chart, but it would be better on a log scale, which works much better for exponential growth, or exponential decline (in module price) for that matter.

(source)