Meet Mary and Tom. Mary lives in a (fantasy) world where income tax brackets are indexed to grow in line with average wages. Tom doesn’t.

A decade from now, Tom will be $25,000 poorer than Mary, even though they both started out earning a pre-tax income of $100,000 (the average full-time wage is $104,765 a year but we’ve used round numbers), and by 2035 they are each on $148,000 having received nominal 4 per cent pay rises every year.