Labour's flagship tax measure is to hit the highest earners with an income tax rise, so as to protect everyone else. Tax will be raised on everyone earning more than £80,000 a year.
Not so fast, says the IFS. While Labour is planning to raise £6.4bn a year from these measures, the think tank warned that just a low level of "responsiveness" - higher earners changing their behaviour, such as by moving abroad - would reduce this to £4.5bn a year. Medium responsiveness would cut it to £2.5bn, and high responsiveness would slash it all the way down - rather improbably - to nothing.