First, I'll go back to this idea of revenue generation. We have a number that we call revenue impact. Last year, it was just under $13 billion, at $12.8 billion. This year, it is well over $13 billion. That number is up roughly 46% over the last four or five years.
Tactically, that's successful. We're getting more taxes for the Canadian public. Strategically, if we continue to find people not complying, we haven't deterred them. The other number we have is the $460 billion that comes in voluntarily, overall. That's the number that really needs to go up. In other words, if we continue to perform audits and we continue to find that taxpayers are non-compliant, there must be something about how we audit or the consequences of audit that isn't getting through, which goes back to the point about criminal investigations and extra penalties for preparers.
In terms of the tax gap, our challenge is about how we allocate those resources. How much do we resource to multinationals? How much do we resource to small and medium-sized businesses? How much on aggressive tax planning? We have to make those judgments, so for us, it's more a question of identifying the eight or nine different tax gaps. How much is in the underground economy? How much is offshore and moving it around? Therefore, for us, it's not necessarily determinative to know how big it is. It's the relative size because our job is to reallocate those resources.
For those countries that do have a measure of tax gap, we have consulted those tax authorities and they haven't found performance lists. Their results aren't up by 46%, after they started measuring the tax gap, so we have been reluctant. Now, under this new government, we have been working and taking steps to understand those challenges and find solutions, so the Department of Finance and the CRA partnered last year to release a number on GST. We're holding a conference this June with experts, academics, and statisticians to understand how we can produce something that might be useful—for you and for the agency—that would make us more transparent.
If we had the answer, the agency would have done it sooner, so now, all I can talk about is our process to come up with an answer.