The total U.S. advertising market rose by nine percent in December, reports advertising spending data provider Standard Media Index. The company attributes advertising spending’s highest level since July 2015 to consumers’ improving outlook on the economy.

After posting strong results during the first two months of fourth quarter 2015, television ad volumes dipped three percent year-over-year in December. Standard Media Index cites challenging ratings seen across many networks for the decline, also noting that spending was potentially affected by advertisers’ decision to ‘front-load’ their spend at the beginning of the holiday season.

In the digital sector, the market jumped by 34 percent in December compared to the same time in 2014—a result that echoed growth rates seen consistently throughout 2015. SMI said the key drivers were content sites (21 percent) and programmatic spending (40 percent), which together made up the majority of digital ad dollars.

SMI’s data also recorded an increase in newspaper advertising during December, but the magazine, out-of-home and radio sectors all posted slight declines. All media sectors ended the fourth quarter with solid year-on-year growth, with the exception of magazines.

“Rising consumer confidence and a positive start to the new broadcast year delivered a strong fourth quarter, which lifted the total market into positive territory following a lackluster first nine months of the year,” says James Fennessy, SMI’s chief commercial officer. “The overall market results were definitely underpinned by excellent NFL ratings and the new dollars from fantasy leagues. On the downside, we see that soft ratings, especially in cable, combined with challenges around digital’s effectiveness caused concerns and this impacted December’s results.”

Advertising investments are in line with U.S. consumer sentiment data recently released by the University of Michigan. Its research showed that sentiment rose in December to its highest level since July 2015, and was lifted by low inflation, modest gains in income and cheaper gas, which has increased Americans' purchasing power.

For more highlights from SMI’s advertising market data, click here.