I've decided I want to move away from index mutual funds and pick the stocks myself. One of the criteria I have is whether or not the firm is union. Is there an easy and reliable way to find this information out? Also, I know some companies are partially unionized. It would be good to be able to find out what the proportion is.
The best way to find out is to ask the company itself. If you read annual reports, there are often mentions of union activities/involvement there. You can also google "[company name] labor union" to see what comes up - news articles generally identify whether the company has a union or not.
But again, the simplest way would be to call/e-mail investor relations at a company and ask about union status.