By Paul Ormerod The precise contents of the budget are still secret. But a widely trailed theme is that the Chancellor, Rachel Reeves, wants to create as much scope as possible for extra public sector investment. She appears to be willing to rewrite the existing fiscal rules in order to accommodate the increase. In principle of course there is a strong case for treating investment in, say, a new road, differently from what is known as current spending. The latter can be thought of as the operational costs of running the public sector, such as the wages and salaries of public servants. A pay ri…