Some of these labourers were so-called "vagrants", farmers who had
secretly left their land or their landlord's land for various reasons,
and had shifted to other regions where they did not register and thus
did not pay taxes. Entrepreneurs liked to hire them for industries
outside the towns where supervision by the government was not so strong;
naturally, these "vagrants" were completely at the mercy of their
employers.

Since _c._ 780 the economy can again be called a money economy; more and
more taxes were imposed in form of money instead of in kind. This
pressure forced farmers out of the land and into the cities in order to
earn there the cash they needed for their tax payments. These men
provided the labour force for industries, and this in turn led to the
strong growth of the cities, especially in Central China where trade and
industries developed most.

Wealthy people not only invested in industrial enterprises, but also
began to make heavy investments in agriculture in the vicinity of
cities in order to increase production and thus income. We find men who
drained lakes in order to create fields below the water level for easy
irrigation; others made floating fields on lakes and avoided land tax
payments; still others combined pig and fish breeding in one operation.

The introduction of money economy and money taxes led to a need for more
coinage. As metal was scarce and minting very expensive, iron coins were
introduced, silver became more and more common as means of exchange, and
paper money was issued. As the relative value of these moneys changed
with supply and demand, speculation became a flourishing business which
led to further enrichment of people in business. Even the government
became more money-minded: costs of operations and even of wars were