Thank you. Once again, that's a very good question.
Measuring language used in the public space is one of the great challenges. Needless to say, while work is a key sector, it's important to understand that one-third of the population is not in the workforce and therefore does not use French or English at work. However, there are other indicators.
The Office québécois de la langue française carried out investigations in 2010 and 2017, in which people were asked what language they used, generally speaking, outside of their home and their circle of friends. According to the results obtained, some people used English more often at home, though they used French at work. Others used more than one language at work, but spoke their other language at home. Of course the language used for service delivery is important. There is also the matter of languages used at performances or a variety of other activities. Indicators could be developed on the use of languages.
People who speak mostly French at home will usually speak French in public. The same goes for people who speak English most often at home.
Nevertheless, the major challenge is to be able to monitor trajectories if we are to acquire a better understanding of the presence of the French language, without falling into a reductionist approach in which those who do not speak French at home are not considered francophones. I think things can be analyzed in a much more subtle manner.