The retirement assets of older Americans surged to a new high of $3.5 trillion last year and, better yet for seniors, those between the ages of 65 and 74 saw the largest increase in wealth of any age group, according to a study by Hearts & Wallets.

The "2014 Portrait of U.S. Household Wealth: Market Sizing, Segmentation and Product Ownership" reported that the retirement income market – households "ages 65 and older that take income at 4 percent or more and are interested in 'retirement income solutions'" – reached $4.7 trillion last year, or 11 percent of all U.S. household assets. This market is predicted to grow to 20 percent in 2020.

The study found that retirement savings jumped to some 33.7 percent of all assets at $13.9 trillion. The retirement assets of seniors between 65 and 74 jumped from $2.3 trillion to $3.5 trillion, which is a new high.