The threat of invasion and the eventual loss of Northern Song territory created a massive influx of people seeking prosperity in the south. The flow of people to the south led to a massive development of southern agriculture. Previously the less populated south would send goods to the north, now with a much more condensed population and development of wet field rice cultivation the farmland in the south was worked to its full potential. These developments led to a “national market place to trade goods” (Lecture 10/12). The government would release illustrated guides to farmers to encourage maximum productivity, “Owning a great deal of emptiness is less desirable than reaping from a narrow patch of land” (Sourcebook 188). In the past an emphasis was placed on owing large quantities of land, now “the secret lies not in expanding the farmland, but in balancing finance and labor, if the farmer can achieve that, he can expect prosperity and abundance” (Sourcebook 189). The constant threat in the north forced the agriculture revolution and one hundred million population enjoyed by the Song dynasty.