It is related to, and at times equated with, theories of Say's law, Ricardian equivalence, and the Policy Ineffectiveness Proposition. Noted macroeconomists such as Milton Friedman and Robert Barro have advocated a weak form of this view, that fiscal policy has temporary and limited effects. Arguments equivalent to the Treasury view are frequently rediscovered independently, and are often in turn criticized by Keynesian macroeconomists. One line of argument is to use the accounting equations in the National Income and Product Accounts (NIPA) to say that, as a matter of accounting, government spending must come from somewhere, and thus has no net impact on aggregate demand, unemployment, or income. Positions on this argument are far apart: advocates of the accounting argument for the Treasury view argue that as a matter of accounting (by definition) fiscal stimulus cannot have an economic impact, while critics argue that this argument is fundamentally wrong-headed and mistaken. A Keynesian reply, by Paul Krugman, is that That is, NIPA accounting equations hold for a "fixed" GDP: the point of fiscal stimulus is to "change" GDP, and that changes in government spending are only exactly offset by decreases in other spending or investment "if GDP is unchanged." Keynesians argue that fiscal stimulus can increase GDP, thus making this point moot. Another Keynesian reply, by Brad DeLong, is that these make assumptions about saving and investment, and ignore basic monetary economics, notably velocity of money: if (for a given money supply) velocity of money increases, (nominal) GDP increases, as GDP = Money Supply * Velocity of Money: a dollar of government spending need not crowd out a dollar of private spending, either as an accounting matter or as a behavioral matter, as it may increase velocity of money. An argument advanced by Milton Friedman in the converse context (fiscal restraint via tax increases having a braking effect, as opposed to fiscal stimulus having a stimulating effect) begins with the NIPA argument above, then continues from the accounting to an economic model: specifically: concluding: and instead advocating monetary policy as the bottom line: This analysis, while disputed by Keynesians (who argue that the effects of fiscal stimulus are more significant than Friedman argues), is considered a legitimate approach, and not dismissed out of hand as wrong-headed.