CEO confidence experienced the largest quarterly gain in the fourth quarter of 2011 at 98.8, up from 83.5 in the third quarter, according to the Vistage CEO Confidence Index.

Because of the boost, the index finds that CEOs are planning increases in employment and fixed investments as they expect higher revenues and profits in 2012. Still, economic and political uncertainty remains the largest concern, which was reported by nearly half of all CEOs. The concern is based on the debt crisis in Europe and the failure of Congress to address the national debt. In fact, two-thirds of respondents say the national debt had negatively impacted their business plans.

Given the increased confidence, 49 percent of respondents say the U.S. will be the most improved economy in the world within three years. Seventeen percent of respondents ranked China as the most improved, and 14 percent of respondent believe South America will be the most improved.