Today the contribution of agriculture to the economy of the region is less significant and the gross value generated by this sector remains slightly above the national average. Marche has never suffered from the extremes of fragmented land ownership or 'latifondo'. Greatly diffused in the past, the sharecropping never produced an extreme land fragmentation. The main products are cereals, vegetables, animal products and grapes. Truffle hunting is popular; although it has often led to 'truffle wars' between hunters due to the imposition of quotas. Olives are also produced and managed by various harvesters. In spite of the marine impoverishment, the sea has always furnished a plentiful supply of fish, the main fishing centres being Ancona, San Benedetto del Tronto, Fano and Civitanova Marche.