The way employees perceive their overall work experience also improved in 2012.

Areas with the highest increases in employee perception scores included effective communication (up 7 percentage points) and business unit/division leadership (up 6 percentage points).

Of course, not everything was rosy.

Engagement scores dropped in terms of employees' sense of accomplishment (down 3 percentage points) and how they viewed their organization's reputation (down 2 percentage points).

Dr. Ken Oehler, Aon Hewitt's Global Engagement practice leader, warned that declining engagement levels may have negative consequences on business performance.

This explains why companies with higher levels of engagement during the recession have seen higher growth in the years since.

Aon Hewitt's analysis showed 2012 engagement scores varied by region. The largest engagement increases were in Europe (improving 5 percentage points to 57 percent) and Latin America (improving 3 percentage points to 74 percent). In North America, engagement dropped slightly from 64 percent to 63 percent, the lowest score since 2008.

Substantial differences in engagement by generation were also identified. Baby Boomers had the highest level of engagement, with 65 percent engaged, followed by Generation X (58 percent) and Millennials (55 percent).

In most regions of the world, ensuring employees believe they have good career opportunities is the best way to drive overall engagement levels up, Aon said.