The notion that the real quantity of money is always at its long-run equilibrium level is associated with the of the price level.

The notion that the real quantity of money is always at its long-run equilibrium level is associated with the classical model of the price level. The fundamental principle of the classical theory is that the economy is self‐regulating that is, the economy is always capable of achieving the natural level of real GDP or output, which is the level of real GDP that is obtained when the economy's resources are fully employed.