As interest rates have plummeted, so investor demand for bond funds has soared. According to several reports, upwards of £1.5bn has been invested into these funds every month since December. Among concerned investors, they appeal because they provide a comparative safe haven seemingly shorn of the inherent risk and volatility associated with equities.

One wonders whether bond funds are merely faddish, or should they form part of every investor’s portfolio?

The case ‘for’ is compelling. Unlike earlier ‘fashionable’ investment trends, investors are not buying into bond funds because they have shown outstanding returns over the last 12 months. On the contrary; their popularity is underpinned by their recent, relatively indifferent, performance.

Two of the most popular funds have been M&G’s High Yield Corporate Bond, which yields approximately 8.4 per cent and the £2.8bn Invesco Perpetual Corporate Bond, currently yielding 6.9 per cent.Significantly perhaps, the performance of both is slightly negative this year but their popularity, driven by solid yields, is understandable as equity investors continue to sit on the sidelines.

One stockbroker, Chris Wilson of Collins Stewart, confirms private investors’ current aversion to equities. He said: “The investment themes that gathered pace towards the end of last year have continued during the opening months of 2009. Investors continue to seek safe havens, such as gilts and gold, and remain fundamentally cautious.”

Indeed, carefulness and prudence have become the investor’s watchwords as people contend with the most severe bear market since 1972-75. By the end of 1974, the FT30 index had fallen by more than 70 per cent from its 1972 peak, and by considerably more in real terms as inflation soared beyond 20 per cent.

It is worth noting that a massive explosion of credit in 1972-73 fuelled a commercial property boom, which ended in bust with a secondary banking crisis. Sound familiar?

“Oh, but deflation, not inflation, is the problem we face today,” you may say.

Do not believe it. As this column predicted last autumn, the UK Government would be forced to start printing money and its direct consequence will be inflation.

Starting the printing presses may be referred to as ‘quantitative easing’ nowadays, but the inflationary impact will be the same, whatever language is used.

The Bank of England’s first asset-buying spree took place last month and more will follow. Bond investors should take note.

Does this mean we should be turning our attention towards the stock market once more?

Bold, less cautious, types argue that average bear markets last for around 18 months, with the most destructive, wealth-damaging, part of it occurring in the final six months.

In the nine months between October 2007 and July 2008, the FTSE100 fell by 22 per cent. During the next four months, it slumped by a further 27 per cent and has remained at roughly the same level since.

Of course, the bullish assumption here is that our current bear market might only have a couple of months to run, but beware and recall what happened between 1930-33, 1972-75, and 2000-03. For the time being, sitting on the sidelines, or investing in bond funds could pay enormous dividends, but when will we know it is time to re-enter the market?

In short, it is impossible to tell, but investors who believe they can ‘call the market’ should consider the statistics covering America’s S&P500, prepared by Global Financial Data for the period January 1982-December 2005, which mirror what happened in the UK.

Over the 23 years, a period of 6,261 trading days, the market’s average annual return was 10.6 per cent. However, had you missed the best ten trading days, your average annualised return would have fallen to 8.1 per cent.

If you were out of the market during its 50 best trading days, that is 0.79 per cent of the total, your annualised return would have plummeted to 1.8 per cent.

In other words, sitting on the equity sidelines is a perfectly reasonable and understandable thing to do, but it is worth being ready for action by remaining relatively liquid, to take advantage when the opportunity arises.