Was going to note that too. I suspect workers are not willing to participate in unions because unions are less able to deliver higher pay (which is a big disincentive for participation). This could be a result of changing labour laws which reduce the fundamental efficacy of unions but regardless the outcome is lower willingness to participate.

Does anyone have the leaked spreadsheet? I’m curious about the other professions and not just the software engineers. I keep hitting a paywall when I follow the links.