The race for Holyrood concludes this week when, on 5th May, voters decide the make-up of the next Scottish Parliament. While politicians compete with new spending pledges, we know that the next five years will be a reality check for devolution. Budgets are falling and the proposals on offer so far – bolder efficiency savings and a public sector pay freeze – won't plug the gap. Nor would the Green Party proposal to use the so-called tartan tax, levying an extra 0.5p on basic rate income tax, get us there. So manifesto commitments offer only a sketchy guide to what will actually happen.