La brita ekonomikisto [[John Maynard Keynes]] argumentis en ''[[The General Theory of Employment, Interest and Money]]'' thatke lowerpli [[aggregate,alaltaj expenditure]]saldonaj inelspezoj theen economyla contributedekonomio tokontribuis aal massiveamasa declinemalpliigo inen incomela andenspezo tokaj employmenten thatla wasdungado wellkiuj belowjam theestis average.sub Inla suchaveraĝo. aEn situationtia situacio, thela economyekonomio reachedatingis equilibriumekvilibron atnur lowje levelsmalaltaj ofniveloj economicde activityekonomia andaktiveco kaj je lataj niveloj highde unemploymentsendungado.
La baza ideo de Keynes estis simpla: por teni personojn tute dungitaj, registaroj devas haltigi deficitojn kiam la ekonomio malrapidas, ĉar la privata sektoro ne investos sufiĉe por teni produktadon je normala nivelo kaj eligi la ekonomion for el recesio. Kejnsismaj ekonomikistoj alvokis la registarojn dum epokoj de [[ekonomia krizo|ekonomiaj krizoj]] haltigi la malaktivemon per pliigo de la [[registaro|registara elspezo]] aŭ per malpliigo de [[impostado]].
Keynes's basic idea was simple: to keep people fully employed, governments have to run deficits when the economy is slowing, as the private sector would not invest enough to keep production at the normal level and bring the economy out of recession. Keynesian economists called on governments during times of [[Crisis (economic)|economic crisis]] to pick up the slack by increasing [[government spending]] or cutting taxes.
AsDum thela DepressionDepresio wore onakriĝis, [[Franklin D. Roosevelt]] triedklopodis, ke la [[publicpublikaj worksvorkoj]], [[Agricultural subsidy|farm subsidies]], and other devices to restart the U.S. economy, but never completely gave up trying to balance the budget. According to the Keynesians, this improved the economy, but Roosevelt never spent enough to bring the economy out of recession until the start of [[World War II]].<ref>{{Cite journal| authorlink=Lawrence Klein|first=Lawrence R.|last=Klein|title=The Keynesian Revolution|year=1947| pages=56–58, 169, 177–79|location=New York|publisher=Macmillan|ref=harv}}; {{Cite book|first=Theodore|last=Rosenof|title=Economics in the Long Run: New Deal Theorists and Their Legacies, 1933–1993|year=1997|location=Chapel Hill|publisher=University of North Carolina Press|isbn=0-8078-2315-5|ref=harv}}</ref>
