Order picking and material handling, in general, have received
considerable attention since the 1970's. It is estimated that
the overall logistics cost in the United States is 21%
of the Gross National Product, and that 28% of this logistics
cost is accounted for by order pick systems (OPSs). There are
more than 300,000 large warehouses with 2.5 million
employees in the United States, and the cost of warehousing
is more than 5% of the Gross National Product. Some
63%
of all operating costs in a typical warehouse can be attributed
to order picking. According to a survey of the Warehouse Education
and Research Council, order picking has been identified as
the
number one area for improvement in warehousing.