The heightened optimism of U.S. investors is reflected in increased net flows into equity mutual funds and ETFs.

Nearly half of U.S. investors are optimistic about the economic outlook in 2013, up 16 percentage points since 2012, according to a new report.

Cerulli Associates discloses this finding in “U.S. Retail Investor Product Use 2013: Impact of Change in Investor Risk Appetite.” Now in its 5th iteration, the annual report examines the behaviors, opinions and preferences related to financial products and services used by U.S.-based investors across the wealth spectrum.

When asked how they view the U.S. economic outlook over the next three months, 48 percent of individuals surveyed by Cerulli say they are optimistic. This contrasts with 41 percent who note they are pessimistic and 11 percent who are unsure.

The 2013 results mark the first time in the five years of the survey when more respondents expressed optimism than pessimism about the economic outlook.

“[This year] has begun with the U.S. equity markets nearing or exceeding their pre-2008 highs, and consumer confidence has risen to new post-2008 highs,” the report states. “So far in 2013, this optimism, combined with a widespread rotation away from fixed income products, has yielded strong results in equity products, potentially just in time for investors to buy high once again.”

The heightened optimism of U.S. investors, the report adds, is reflected in increased net flows into equity mutual funds and exchanged-traded funds. In 2012, net flows totaled $66 billion, up from $11 billion in 2011, though down from the $101 billion recorded in 2010.

The report notes, however, that most investors approaching retirement are still struggling to sustain reliable retirement income. Of the nearly 25 million U.S. heads of households ages 50-59, about 21 million have accumulated less than $500,000 in investable assets.

“While these individuals generally have several years to continue adding to their retirement assets, they face an uphill struggle, especially considering widespread expectations of challenging equity returns and expected interest rate increases,” the report states. “Frankly, even those who accumulate $1 million in retirement assets will likely be underwhelmed by generally accepted guidelines of only expecting $40,000 to $50,000 in annual income on such an asset base.”