There's some current dialogue about some big tech companies (google, twitter, facebook) displaying some bias in their actions. Whether that's true or not, it certainly seems that the composition of those companies' workforce leans heavily left.
There are other industries or companies that also seem to slant heavily left or right; for example, journalists lean heavily to the left while industries from the farming, fossil fuel and construction sectors lean right, according to donations to parties in USA (see this link for more details - the IT sector leans somewhat left). Are there any good studies that explain why this happens? It seems odd that certain jobs would appeal to people based on their political preferences, but perhaps that happens. Perhaps one's profession influences one's political beliefs? Or perhaps there's a founder effect, and that as industries grow, people join (and remain with) companies that have a compatible belief structure?
To sum up: I'm asking if there's any good research pointing to why so many organizations' workforces tend toward one extreme or the other, instead of representing a statistical mean of the population. I'm especially interested in organizations that aren't innately political in and of themselves, but where the shift happens more organically.