U.S. investor optimism declined sharply this month according to the UBS/Gallup Index of Investor Optimism.

The index dropped all the way to 52, down from 74 last month. UBS reports that this is the first time the index has fallen below 60 since September 2003, when the overall index was at 54. Conducted monthly, the Index had an initial baseline of 124 when it was established in 1996.

The decline in opinions about the economy was fueled primarily by the recent drop in the stock market, but also by increasing concerns about inflation, UBS notes. Investors remain more optimistic than pessimistic about the performance of the stock market, with 41% optimistic and 33% pessimistic. But that 8-point net positive optimism is down from a 20-point net positive feeling measured last month, when 47% were optimistic about the stock market and just 27% pessimistic. It notes that there are also increased concerns among investors about meeting their short-term investment goals and about maintaining their income.

Despite the index’s decline, the survey shows little change in investors’ expectations for return on their investments over the next year, UBS points out. The average expected return is 9.9 %, little changed from last month’s 10.3%.

The percentage of investors who say that now is a good time to invest in the markets continues its slow decline – 57% express that view, down from 60% last month and 64% in December.

This month, investors were also polled about Social Security and a proposal to divert part of Social Security taxes into a personal retirement fund. The poll shows that over the past five years, there has been a significant erosion in support for such a plan.

Today, 50% of investors want to continue with the Social Security system as it is, with all Social Security taxes paid into the system. Another 47% opt for taking a portion of their Social Security taxes and putting them into a personal savings account for retirement.

When the question was first asked in June 2000, investors preferred the personal retirement account proposal by a substantial majority, 60% to 36%. A year later, support had eroded somewhat, with 54% in favor and 42% opposed. This past January, investors were more divided, with 49% supporting the personal retirement accounts, and 46% the status quo. This is the first time the Index has shown more investors preferring the status quo over the personal retirement proposal.

The only proposal in the survey supported by investors is to raise taxes on people with incomes of $500,000 a year or more — 75% of investors think that is a good idea, 23% a bad idea. Support for raising Social Security taxes has increased somewhat over the past five years, from only 19% in 1997 to 34% now.

These findings are from a survey conducted from April 1 to April 17.