dynasty, many shops opened. Often, shops selling the same product were concentrated into one urban area. For example, all the rice shops would occupy one street, and all the fish shops another. Unlike the later Ming dynasty, most businesses during the Song dynasty were producers and retailers, selling the products they produced, thus creating a mixture of handicraft and commerce. Although the Song dynasty saw some large enterprises, the majority of enterprises were small. Overseas commerce also prospered with the invention of the compass and the encouragement of Song rulers. Developments in shipping and navigation technologies allowed trade and investment on a large scale. The Song-era Chinese could conduct large amounts of overseas trade, bringing some merchants great fortune. Song-era commercial enterprises became very complex. The accumulated wealth of merchants often rivalled that of the scholar-officials who administered the affairs of government. Song currency The prosperous Song economy resulted in an increase in the minting of currency. By 1085, the output of copper currency reached 6 billion coins a year, compared to 5.86 billion in 1080. 327 million coins were minted annually in the Tang dynasty's prosperous Tianbao period of 742–755, and only 220 million coins minted annually from 118 BCE to 5 CE during the Han dynasty. Paper receipts of deposit first appeared in the 10th century, but the first officially sponsored bills were introduced in Sichuan Province, where the currency was metallic and extremely heavy. Although businesses began to issue private bills of exchange, by the mid-11th century the central government introduced its paper money, produced using woodblock printing and backed by bronze coins. The Song government had also been amassing large amounts of paper tribute. Each year before 1101, the prefecture of Xinan (modern Xi-xian, Anhui) alone sent 1,500,000 sheets of paper in seven different varieties to the capital at Kaifeng. In the Southern Song, standard currency bearing a marked face value, was used. However, a lack of standards caused face values to wildly fluctuate. A nationwide standard paper currency was not produced until 1274, two years before the Southern Song's fall. Song fiscal administration The Song government instituted a taxation system on agriculture in which a property value tax was collected twice every year, amounting to roughly 10% of income. However, the actual level was higher due to numerous surcharges. Commercial taxes were around 2%. In an important change from Tang practices, however, the Song did