A boom in tablet sales helped digital magazines boost their share of total magazine sales in the first half of the year, although growth has slowed and is failing to offset declines in print, according to the latest ABC figures. Digital sales increased 26 percent year-on-year to 369,040 -- down from the 59 percent growth seen last year, due to a slowdown in magazines reporting digital sales. Digital publications make up 2.9 percent of magazines' circulation, up from 2.3 percent a year ago.