I'm pretty sure the data is coming from the self-reported salary spreadsheet that was posted on here about a month ago (https://news.ycombinator.com/item?id=11331223). There's a lot of valuable information in it and there were no geographical restrictions on participation. However, it's all self-reported and unverified, and there are some values that are obvious fakes.
It's possible that some of the data came from that spreadsheet. The sources of the data are cited at the bottom of the post. You're right that it is all self-reported and unverified. We tried to clean and standardize the data as best we could. The biggest source of error for us in the process might have been the level, particularly because some of the reported bonuses and stock compensation seemed out of line with the stated level. But we took the Level as it was in almost all cases. It may very well be that companies overpay in certain circumstances.
Wired-Logic uses a GIF as output.
Interesting take on making AND and XOR gates, makes it a bit more colorful.