Yes, I know this is axiomatic - everyone but Labour knows this. Let's just take the effect on one sector of the economy - private education. As this piece in the Telegraph graphically describes, high earning parents want their kids in private schools, and "Parents would rather crawl over broken glass than take their children out of independent schooling".
Now like them or not, the private schools turn out large numbers of well rounded highly qualified young people. Not to say they don't come out of the State sector as well - some decent LEA schools produce outstanding pupils, but consider that Eton got more GCSE A grades last year than the whole of the borough of Tower Hamlets.
Overall, higher tax rates with no tax exemptions for school fees will tend to depress the quality of pupil output as the private sector shrinks and the poorly performing State sector grows. And of course all the pupils taken out of private education will now have to be educated at the taxpayer's expense. Both ways we become marginally less competitive as a nation.
So long term losses in return for short term electoral gains. Isn't that Liebour all over?