INDIANAPOLIS (AP) _ The state’s portion of gambling revenue is slumping as Indiana’s 13 casinos take advantage of a new law that allows them reduce their tax burden.
 
  A report released Monday shows total tax receipts from casinos last month fell nearly 18 percent compared to May of last year. Gaming commission deputy director Jenny Reske tells The Indianapolis Star that much of that drop resulted from casinos deducting free-play coupons used to attract gamblers, as allowed under a law passed by this year’s General Assembly.
 
  Horseshoe Casino manager Daniel Nita says the move should help Indiana casinos be more competitive with those in neighboring states.
 
  Reske says some companies own casinos in Indiana and competing states.
 
  Despite the relief, casino revenues dropped 5.8 percent from May 2012.