David Robinson used the data from the 28,657 people who self-selected to take the Stack Overflow survey to investigate the relationship between programmer pay and the conventions of using either tabs or spaces to mark indents, and found a persistent, significant correlation between using spaces and bringing home higher pay.
Did we see the same tabs/spaces gap within each of these groups?
Yes, the effect existed within every subgroup of developers. (This gave a similar result even when filtering for developers only in a specific country, or for ones with a specific range of experience). Note that respondents could select multiple languages, so each of these groups are overlapping to some degree.
I did several other visual examinations of possible confounding factors (such as level of education or company size), and found basically the same results: spaces beat tabs within every group. Now that the raw data is available, I encourage other statisticians to check other confounders themselves.
Developers Who Use Spaces Make More Money Than Those Who Use Tabs [David Robinson/Stack Overflow]