However, red flags remain. The same polling data suggested the U.S. labor force is now further disenchanted with their opportunities for advancement, financial compensation, health care coverage, and, particularly, task-driven stress. Commenters' feelings about vacation time and workplace harmony, while positive (co-worker relations overwhelmingly so), remained relatively unchanged.

Gallup's polling numbers correspond with the results of other recent reporting data regarding worker satisfaction within the United States. In July, the Conference Board's annual Consumer Confidence Survey found almost one-half of employees questioned professed a positive outlook. That represents the highest figure noted by the firm since 2005.

Related: How to keep employees happy

Gad Levanon, chief economist for the Conference Board North America, credits the trends to an improving economy. "The rise in workers' job satisfaction is directly influenced by labor market improvements," says Levanon. "The rapidly declining unemployment rate, combined with increased hiring, job openings, and quits, signals a seller's market, where the employer demand for workers is growing faster than the available supply."

"In these labor market conditions workers are more satisfied with their jobs in several different ways. These include layoff rates and greater job security, more job opportunities and more job switching, increased wages and increased employer efforts to retain workers," he says.

However, while the authors of the Gallup study, Frank Newport and Jim Harter, also said they believe that rising wages and overall economic stability have contributed to the gains observed in worker contentedness, they caution that satisfaction in itself is of limited benefit to companies concerned with maximizing productivity.

Specifically, the Gallup report highlights the still-depressed levels of worker engagement within the United States. Despite the sizable upswing in satisfaction, Newport and Harter classify nearly two-thirds of American workers as something other than actively engaged with their careers.

Related: Fewer employers spending on employee engagement efforts 

"Engaged employees," wrote Newport and Harter, "are involved in and enthusiastic about their work and workplace. They are more likely to show up to work, are less likely to leave the organization, treat customers better and are more productive." In the absence of engagement, they contend that even satisfied workers will be considerably less likely to contribute more than minimal effort aimed at retaining additional wages or benefits.

Unfortunately, whereas workplace satisfaction to some extent seems a natural consequence of rising economic fortune, the study's authors argue that effecting engagement among a company's labor force requires a multi-layered, systematic approach to foster a sense of shared purpose. "This type of focus on engagement," Newport and Harter conclude, "can have a powerful effect on the factors that matter most to an organization's performance management and human capital strategies."