<P> A second type of market that developed in China was the urban - rural type, in which rural goods were sold to urban dwellers . This was particular the case when landlords decided to reside in the cities, and use income coming from rural land holding to facilitate exchange in the cities . Another way this type of market was used was professional merchants who bought rural goods in large quantities . </P> <P> The third type of market was the "national market" which was developed during the Song dynasty but particularly enhanced during the Ming . This market involved not only the exchange described above, but also products produced directly for the market . Unlike earlier dynasties, many Ming peasants were no longer producing only products they needed; many of them produced products for the market, which then they sold at a profit . </P> <P> In the early Ming, after the devastation of the war which expelled the Mongols, the Hongwu Emperor imposed severe restrictions on trade (the "haijin"). Believing that agriculture was the basis of the economy, Hongwu favored that industry over all else, including that of merchants . After his death, most of his policies were reversed by his successors . By the late Ming, the state was losing power to the very merchants which Hongwu had wanted to restrict . </P> <P> The Ming dynasty also engaged in a thriving trade with both Europe and Japan . The amount of silver flowing into the Ming dynasty was estimated by Joseph Needham at 300 million taels, which is equivalent to more than 190 billion dollars in today's money . In addition to silver, the Ming also imported many European firearms, in order to ensure the modernness of their weapons . </P>

What was the official trading policy of the ming dynasty