Source: United Nations Office for the Coordination of Humanitarian Affairs, Occupied Palestinian Territory (OCHAOPT) http://www.ochaopt.org/default.aspx 
As the Blockade was stepped up in June 2007 it resulted in a decrease of imports through the border crossings by approximately 80%. In spite of the easing of the blockade policy, as a result of the massive international criticism in connection with the first Flotilla, mainly concerning import of merchandise, this import has remained at a level of only 40% of what it was before the Blockade.
IDF (Israeli Defence Force) has never been willing to conjure a list of which necessities are blocked at the bordeer crossings during the various periods. The Israeli peace organisation Gisha made such a list in June 2010 based on information yielded by the UN, the Red Cross and other relief organisations: http://www.gisha.org/[...]/Products060610_Eng%281%29.pdf