Valero Energy Corp. is selling oil refineries that it had bought a few years ago.  We used to have a shortage of domestic refining capacity, but now we have an excess—even though there has not been a new refinery built in the United  States in years.  Capacity at existing refineries was expanded through new technology, our demand for refined products lagged, and imports of refined products have increased, thanks to expanded capacity overseas.  (It used to be that only crude oil was shipped in, but now gasoline and diesel are imported in tankers.)