[httpz]

It's not completely arbitrary. Where the HQ is usually shows where the company got started and experienced its initial growth. Also, while a company may have multiple remote offices, most execs will be in HQ and that can have a huge impact on the culture of the company. A Google office in Japan may feel more like a Silicon Valley company than a Japanese company's office in Silicon Valley.

[RobLach]

I do believe that but this particular data set will demonstrate very little evidence of that since since the very likely biggest reason Y Combinator companies seem to be centered around SV is because that's where SV is; and so the data is biased beyond usability in this manner.