The four pillars of the Egyptian economy are oil and gas, Suez Canal revenues, remittances from Egyptians working abroad and tourism. The resources are vast, but the ever-increasing population eats them all up. Egypt had been a feudalist economy for a very long time and prior to the revolution of 1952, its economy was based primarily on farming, with very little industry.  The 1960’s saw an increase in industrialization with the construction of the Aswan High Dam. Under Gamal Abd-El Nasser's socialist regime, the majority of large industries were nationalized. In the 1970's President Anwar El-Sadat introduce his "Open Door Policy" which encouraged a free market as well as trade with Europe and the United States.  This gradual economic reform has been continued by President Hosni Mubarak and the 1990's have witnessed a high degree of privatization, in an effort to diminish Nasser's public-sector and introduce a new flourishing private-sector with its own new stock exchange in down town. The Egyptian currency is the pound. It comes in half-pound notes, one-pound notes, five-pound notes, ten-pound notes, twenty-pound notes, fifty-pound notes and one hundred-pound notes.