That's an excellent question. In the Canadian census, the words "francophone" and "anglophone" appear nowhere. We ask a question about the language which was first learned. It might be French, English or another language. In a significant number of cases, people have two mother tongues, namely English and French. So someone has to decide, but it is not necessarily us. Some people choose to use this double category; others place people under "French", and yet others under "English". Statistics Canada publishes information based on the census, but nowhere does the census form define what a francophone or an anglophone is.
I will answer the second part of your question. The situation has changed greatly in the past five years. In fact, this is mainly due to the strong increase in immigration. I mentioned that Canada received 1.1 million new immigrants in the last five years. The relative importance of English as mother tongue has decreased, as has the relative importance of French as mother tongue. It is the most significant decrease we have observed in the last few years.
As for whether the number of francophones has increased, if you use the mother tongue criteria, there is definitely a decrease, with regard to both English and French. However, Quebec anglophones identify with the concept of first spoken official language, since approximately 13% of the anglophone population indicates English as being its first official spoken language. However, if you use the criteria of mother tongue, it would be 8.1% of the population.
This is the choice made by people living outside Quebec. Some prefer using the mother tongue to define francophones. In Ontario, some people prefer to use only the criteria of French spoken in the home. That would bring down the number from 500,000 to 300,000 people. That is why Statistics Canada does not provide a definition.