I'm not sure about that.
I think the drop in the maximization rate has much more to do with the fact the maximum you can put in has grown by $5,000 a year. When the total amount you could ever put in a TFSA was $5,000 or $10,000, you saw much higher maximization rates. Now, once you're at $36,500, people are less likely to have that much money lying around that they could put in a TFSA. It's not surprising at all that folks in the lower-income bracket who are making the bottom 10%, or who are making under $5,000, don't have $5,000 a year to put into a TFSA, which is why you see the maximization rates extremely low at 1%.