By Hal M. Bundrick NEW YORK ( MainStreet)--Not only is cash king, its reign is vast. An overwhelming 88% of one firm's investors are holding an average of 20% of their portfolio in cash. But apparently these investors will be looking to put some of this liquidity to work, as the survey of Fidelity Investments customers with at least $250,000 in investable assets also found that high-net-worth individuals are optimistic about the market. 81% believe the Dow Jones Industrial Average will be up at the end of 2013. "Investors feel optimistic that the economic recovery in the U.S. is under way, yet the memory of the market downturn is causing that optimism to be tempered," said John Sweeney, a Fidelity executive vice president. "As investors feel more certain about job growth, encounter strong corporate earnings and better understand fiscal policy changes, they will invest in the market with more confidence. That confidence leads to better decision making and enables investors to withstand volatility in the market."