I think it very much depends on which country you're in on the legality of this. In the United States discriminating in the hiring based on these is illegal and

I think it very much depends on which country you're in on the legality of this. In the United States discriminating in the hiring based on these is illegal and even asking these questions as part of the hiring process can be highly suspect as it does open up a cause of action for you to indicate potential discrimination. Now, there are exceptions to that if race and gender fundamental requirement for the job. For example if you are casting for a movie or play the parts could have very specific race, gender, age requirements. The vast majority of jobs this is not the case. I would absolutely refuse to answer any question in regards to this prior to hiring. Once I was hired it becomes a different matter. As others have pointed out there are legal reporting requirements companies must follow that include this data. But this data should not be used prior to hiring nor should it need to be known.