The '''Lucas aggregate supply function''' or '''Lucas 'surprise' supply function''', based on the '''Lucas imperfect information model''', is a representation of [[aggregate supply]] based on the work of [[New classical macroeconomics|new classical]] economist [[Robert Lucas, Jr.|Robert Lucas]]. The model states that [[economic output]] is a function of "money" or "price "surprise." The model accounts for the empirically based trade off between output and prices represented by the [[Phillips curve]], but the function breaks from the Phillips curve since only unanticipated price level changes lead to changes in output. The model accounts for empirically observed short-run correlations between output and prices, but maintains the [[neutrality of money]] (the absence of a price or money supply relationship with output and employment) in the long-run. The [[Policy Ineffectiveness Proposition|policy ineffectiveness proposition]] extends the model by arguing that, since people with [[rational expectations]] cannot be systematically surprised by [[monetary policy]], monetary policy cannot be used to systematically influence the economy.
