Major U.S. retailers hit the accelerator in December by increasing the total number of ads across several platforms by 19 percent, according to the ABX Advertising Benchmark Index. ABX also said in its monthly report that Kohl’s Corp. took the top spot in television ad effectiveness while Wal-Mart Stores Inc. was number one in digital and J.C. Penney & Co. was first in print.

ABX measures 14 variables, with a consumer panel rating each ad for the month. A score of 100 equals “average effectiveness” of an ad. The ABX Index is the most important score for an ad’s overall effectiveness, noted the company’s researchers.

For December, retailers ran 681 new ads, which compares to 574 in November. Kohl’s “Get to Kohl’s and Seize These Saturday-Only Deals” was the most effective television spot during December. Its ABX Index measure came in at 134, and was bolstered by a reputation score of 180 and an action score of 165.

“While Kohl’s beat 143 TV ads with this simple, clean ad, it is worth noting that three other TV spots came very close to winning, as well,” the ABX researchers said, adding that Sears’ “Quick Before Santa Sees” spot scored high as well as Target’s “Welcome Back to the Red” ad. Kohl’s “My Name is Charlene” TV ad also scored high.

“All three had strong Christmas imagery and special creative approaches,” the ABX researchers said. “Kohl’s winning ad has simply refined the sales message both vocally and graphically to be so clear, it is hard to resist, and the clean-cut kids featured in the ad likely impacted [the] reputation [score].”

In the digital ad segment, Wal-Mart’s “Great Training Leads to…” video was number one with an ABX Index score of 132, and a 223 reputation score. “Wal-Mart shares its education process to train its associates through a very in-depth process, enabling employees to have big opportunities,” ABX researchers noted in their report. “The employees depicted in the segment were clearly proud of themselves and their progress; a real ‘feel good’ moment.”

ABX also said that with its Gender Equality Measure, the Wal-Mart video scored a noteworthy 110, “which means that females were presented with respect in this fine spot.” ABX said that the GEM score “directly impacts reputation and action scores, and is part of the #SeeHer effort from [the] Alliance for Family Entertainment and [the] Association of National Advertisers.”

For radio, Sam’s Club’s “Your Pizza Night Just Got Easier” spot was number one with an ABX Index score of 120. “This spot scored way above other retailers and the reasons are pretty obvious,” the ABX researchers said. “The voice-over talent has a clear, calm voice that invites the listener to pay attention.” For print ads, J.C. Penney took the top spot with its ad touting shoppers to take “Extra 5% Off Military Discount.” The ad had an ABX Index score of 126.

“J.C. Penney’s reputation scored a big 46 percent over norm with this special 5 percent off sale for military service members,” the researchers said. “There is nothing of graphic importance to the ad itself, but the headline and purpose of the ad enables a very clear message at 29 percent over norm and [an] action [score] at plus-49 percent.”

For free-standing inserts, Kroger’s “Buy 4, Save 4, Mix & Match” was number one while its “Click List” billboard was tops in the out-of-home ad category.