WASHINGTON - For what may by the first time, the number of H-1B petitions withdrawn by applicants or rejected by U.S. authorities is exceeding the number of new petitions for the visas. The numbers have resulted in a slight decrease over the past two months in the H-1B visa petition count on the scale of a rounding error. The drop may be little more than a short-term phenomenon, but it is inviting theories as to its cause, ranging from increased U.S. scrutiny of the H-1B petitions to the general economy.