In the southern areas of Europe, where Jews had long been settled, Jewish
economic activities were relatively diversified. In the north, where Jews were often
invited by rulers to fill perceived lacunae in the local economy, Jewish economic
activities tended to be fairly limited. These Jews were unable to break out of these early
constraints and diversify into the local economies.

During the eleventh century, the limited Jewish economic contribution was
centered in trade. As the European economy began to accelerate during the twelfth
century, a new, rewarding, but problematic economic specialization emerged. The
acceleration of the European economy coincided with an increasingly aggressive and
effective Church hierarchy. One of the campaigns upon which Church leadership
embarked was the effort to stamp out the sin of usury, defined as Christian taking interest
from Christian for the lending of funds. The combination of Church curtailment of
Christian lending and of the growing need for the transfer of capital opened the way for
Jewish lenders to provide the flow of capital required for increasingly ambitious projects
of all kinds.

To be sure, money-lending has never been a popular profession. Banking has
always aroused considerable popular animosity. Such economically-grounded animosity
readily combined with traditional imagery of Jewish enmity, with each reinforcing the
other. A sense of the Jews as expressing their hostility toward Christianity and Christians
through financial exploitation and manipulation became common throughout western
Christendom.