Roughly half of the OECD countries do tax gap measures. A couple of years ago, the OECD put out a very good report, assessing the different efforts. The Canadian Parliamentary Budget Office did make use of the best-case efforts, looking at other countries, and have done some work on a tax gap report, but couldn't complete their study because of certain CRA information they would still need.
It wouldn't take much for the government to provide that information. We could have a report that could be very helpful in helping CRA to know where to focus their efforts.