American consumers are the sunniest they've been in more than 15 years.

The Conference Board said Tuesday that its consumer confidence index climbed to 113.7 in December, up from 109.4 in November and the highest since it reached 114 in August 2001.

The index measures consumers' assessment of current conditions, which dipped from November but was still very positive, and their expectations for the future, which hit a high.

Director of economic indicators at the Conference Board Lynn Franco said the "post-election surge in optimism" was strongest among Americans who were older.

Later on Tuesday, Trump thanked himself for the consumer confidence surge. He took to Twitter to note that the numbers of confidence levels are the highest the index has climbed in more than 15 years. Trump added, "Thanks Donald!"

The U.S. economy grew at a 3.5 percent annual pace from July to September, fastest in two years. Unemployment is at a nine-year low of 4.6 percent. Employers have added 180,000 jobs a month this year, down from an average 229,000 in 2015 but still solid.

"The election of Donald Trump has raised household expectations for the economy to a very high level," Stephen Stanley, chief economist at Amherst Pierpont Securities, wrote in a research note. "It remains to be seen whether Trump can deliver," but the burst in confidence could drive consumer spending higher.

The Associated Press contributed to this report.

