LONDON (Reuters) - Investors' increased their allocations to cash and reduced their an overweight position in stocks in August, as expectations for global growth dropped to its lowest in 8 months, a BofA survey of fund mangers published on Tuesday showed.

According to the survey, 31% of respondents said they were overweight stocks in August, down from 51% in July, while their average cash level was 4.3% of their assets under management, up from 4.1% a month before.

BofA attributed the shift to weak U.S. payrolls data for July, and the volatility shock associated with the rebound in the yen.

BofA said 189 participants with $508 billion of assets under management responded to the survey.

A net 47% of survey respondents expect a weaker global economy in the next 12 months, down 20 percentage points from July.