People in the workforce are getting more optimistic about the economy and their retirement, but people in retirement aren't as hopeful, according to a new poll by Wells Fargo.

This follows a period when both groups were pessimistic, according to the Wells Fargo/Gallup Investor and Retirement Optimism Index.

Investor optimism rose to 31 on the index in March, up from a minus eight in November, according to a survey of 1,035 retired and non retired investors. The Wells Fargo survey set a baseline of 124 when it was started in October 1996. It hit a high of 178 in January 2000 and a low of minus 64 in February 2009.

In November, the optimism index was at minus eight for non-retired people and that jumped to 38 this spring. For retired Americans, the measure rose from a minus five in November to 7 in March.

Half of retired investors say the low interest rates have done a great deal or quite a lot of harm to savers and investors while only 25 percent of non-retired investors feel that way, according to the survey.

At the same time, 43 percent of all investors (35 percent of retired and 46 percent of non-retired) fear low rates will mean they will outlive their money in retirement, the survey shows.

While overall optimism is growing, 54 percent of non-retired investors think it is a good time to invest in the market and 43 percent of the retired feel the same. But most (85 percent) say they have made no changes to their investments so far.

Taxes are a worry to both groups. Seventy-one percent of non-retired and 59 percent of retired are worried they will have to pay higher federal taxes in retirement and will have a more difficult time living comfortably. For 39 percent, that worry has translated into seeking after-tax investments.

Sixty-one percent f non-retired investors saying they have no worries about being unhappy in retirement and 69 percent of retired people saying they are not worried.