I'm a statistician; I do this as.... I was paid once by a maritime province to work out the assets of people who get GIS. I accessed StatsCan data, and you could do it. You could say that we are not going to pay GIS to somebody who lives in a $500,000 or an $800,000 house.
To do that you're going to have to collect that information and then train auditors, who are going to make sure that all of that asset information is accurate for the million and a half GIS recipients.
How many of them are sitting on substantial assets but have no income? I just don't think it's worth the effort to collect all that—ask that information, hire auditors, and then of course set up a bunch of rules such that people start hiding assets: “I can get a GIS if I sell my house to my children now.”