While scholars agree that the crusades had an economic impact on medieval Europe, they do not agree over the nature and extent of that impact.

Malcolm Barber, in The Two Cities, Medieval Europe 1050-1320 (Routledge, 1992), p. 139: 'During the twelfth and thirteenth centuries the crusading movement was responsible for fundamental changes in western Christendom, for to enable tens of thousands of men and women to travel to and from Palestine, Syria, Cyprus, Egypt and Greece, and to move their horses and supplies, involved a revolution in transportation, finance and government so profound that it must be accounted a major reason for the transformation of the nature of western European society and its economy from that of the early medieval world.'

See Giles Constable, 'The Financing of the Crusades in the Twelfth Century', in Outremer. Studies in the History of the Crusading Kingdom of Jerusalem presented to Joshua Prawer, ed. Benjamin Z. Kedar, Hans Eberhard Mayer and R. C. Smail (Jerusalem, Yad Izhak Ben-Zvi Institute, 1982), pp. 64-88.

See also Simon Lloyd, 'The Crusading Movement, 1096-1274', in The Oxford Illustrated History of the Crusades, ed. Jonathan Riley-Smith, OUP, 1995, pp. 34-65: (p, 56) 'Perhaps the most significant change in crusade financing in these centruies lay in the emergence of secular and ecclesiastical taxation specifically for purposes of crusade. In part, this was a function of the experience of the very earliest crusades, notably the First, which taught how expensive crusading was in practice, but it was also a development that could not have occurred without considerable growth in the notions and apparatus of the secular state and papal monarchy, attendant centralisation and administrative sophistication, and greater refinement in the concepts of crusade and Christendom.'

So the development of systems of taxation was both a result of changes in western European society and a catalyst of change. But: (p. 65) 'The need for weapons, foodstuffs, and other necessaries also provided temporary growth in demand in crusaders' homelands for a whole range of items, although it is impossible to know whether the economic stimulus stemming from expenditure for the crusades was outweighed by the disruption that crusading also caused to economic life.'

In short, the economic impact was both positive and negative. The merchant cities of Italy: Genoa, Venice and Pisa, benefitted from their trading rights in the Latin East. Yet the wars with Egypt and Syria also damaged their trade.