One newspaper story said that an oil refinery in southern Iraq was operating at a small part of its normal capacity, because the refinery needed a lot of water, but the water purification plant had been looted; every pump and moter from the water purification plant had been stolen. This makes no sense. Ordinary people have no use for industrial pumps and motors, and therefore have no incentive to steal industrial pumps and motors.
I recall two stories about the postwar occupation of Germany. The first story was about some american soldiers who were assigned to study the german me262 jet airplanes. When the americans went to the me262 factory and test site, there was nothing except some disassembled airplanes, missing some important parts. The tools and spare parts were gone. But eventually the americans won the trust of the german workers, and the german workers brought back all the tools and spare parts, and put the disassembled airplanes back together. (I think I read that story in Smithsonian Air and Space magazine.) The other story was a biography of a west german postwar industrialist. His first job in 1946 was as a diver. He would dive into rivers and ponds with a rope, and tie the rope onto various machines, so that the machines could be pulled out of the water. (I think I read that story in Forbes magazine.) Many things were missing in postwar Germany. But the missing things were hidden, not stolen. The germans hid things for two reasons. First, the germans were trying to keep things away from their enemies. The second, and more important reason, was that the germans were trying to protect things, so that things would not be destroyed in the war.
I think the same is true of Iraq. I think that many things which are missing in Iraq have been hidden by the people who worked with those things. So I think that the pumps and motors missing from the water purification plant in southern Iraq have been hidden by the people who worked in the water purification plant. So the occupation authority does not need a stronger policy against looting. The occupation authority needs to work harder at gaining the trust of the Iraqi people, so that the people will bring the missing things back.
After the fall of Bagdad, it was reported that a museum in Bagdad had been looted and everything had been stolen, and many people criticized the Bush administration for not securing the museum. But later it was reported that the museum staff had hidden most of the museum contents before the fall of Bagdad, and eventually brought most things back. So it would have been pointless for the Bush administration to secure the museum, because the museum staff had already secured the museum contents, and the museum was already empty.
Things which can be used by ordinary people like food and cars probably were stolen. And some Iraqis are apparently destroying things to prevent the americans from using those things; this is a problem which does require better security. But anything which is missing, not destroyed, and not useable by ordinary people has probably been hidden, and will be returned eventually.