Sponsors who left Fox News star Laura Ingraham’s show at the behest of teen gun control activist David Hogg are missing out on a 20 percent increase in eyeballs. The conservative author of “Shut up and Sing” lost nearly 30 advertisers since a boycott against her show launched March 29, but those who held firm are benefiting from a ratings windfall. Data compiled by the media watchdog News Busters shows a jump from 2.23 million viewers prior to Mr. Hogg’s campaign to 2.7 million since her return from a vacation.