How much allowance should I get?

Hey, im 15, going into grade 10 next school year. My older sister and I have both been getting 40$ each a month for the last few years, and im wondering if this is too much or too little. I get decent grades (average 80%) and my sister gets very good grades. We deal with the dishwasher, help with dinner, sometimes make dinner, mow the lawn, clean the fishtank and other general chores. Also, we live in Canada in case that makes a diff.