Jimmy Fallon quickly closed the ratings gap between him and new "Late Night" host Stephen Colbert. On the second night of NBC's "The Tonight Show Starring Jimmy Fallon" going head-to-head against CBS' "The Late Show with Stephen Colbert," Colbert narrowly beat out Fallon in household ratings, but Fallon won the race in one key demographic, 18-49-year-olds.

After a strong debut, Colbert shed 35 percent of his audience in the coveted 18-49 demo and lost to Fallon although he maintained a slight edge in the early metered market household ratings, according to The Hollywood Reporter. Colbert's overnight rating dropped from a 4.9 to a 3.2 in households while Fallon jumped from a 2.4 to a 3.1 rating.

In the very important 18-49 demographic "The Tonight Show" stayed steady with a 1.2 rating while "The Late Show" saw a rating of 0.8, according to Entertainment Weekly. Fallon's show saw its rating go up on account of guest Justin Timberlake, who joined the host for a sixth edition of their "History of Rap" segment. 

CBS did however state that "The Late Show's" household rating was up 113 percent compared to the same night in 2014 when David Letterman was still the host, reported Variety.