NEW YORK — According to a report in today’s Sports Business Daily, NBA viewership was down sharply during the ’12-13 regular season. TNT: After two straight seasons of record figures, TNT saw its average rating down 18% and viewership down 20%. In addition to a lockout-shortened season in ’11-12, several other factors helped contribute to the decline. Superstorm Sandy knocked out many homes in the Northeast at the start of the season. Some 16.9 million homes, including many in N.Y., Boston and