The period from 1948 to 1956 saw extensive attempts by Palestinians to cross the border, which were met by severe violence by border guards and a corresponding increase in the violence of border-crossers (residential, political and criminal). From 1967 to 1993, a period of mass employment in Israel of Palestinian workers from the Israeli-occupied West Bank and Gaza Strip prevailed, although immigration and naturalization remain largely inaccessible. During the 1990s, escalating policies of closure of the Green Line replaced labor mobility. In the 2000s, this policy has been supplemented by physical barriers in the West Bank and Gaza, and increasingly tight restrictions on family reunification.