Norway developed market towns at a much later period than other parts of Europe. The reasons for this late development are complex but include the sparse population, lack of urbanisation, no real manufacturing industries and no cash economy. The first market town was created in 11th century Norway, to encourage businesses to concentrate around specific towns. King Olaf established a market town at Bergen in the 11th century, and it soon became the residence of many wealthy families. Import and export was to be conducted only through market towns, to allow oversight of commerce and to simplify the imposition of excise taxes and customs duties. This practice served to encourage growth in areas which had strategic significance, providing a local economic base for the construction of fortifications and sufficient population to defend the area. It also served to restrict Hanseatic League merchants from trading in areas other than those designated.