When investors put their money in the stock market, they are frequently told it should be for the long haul.

But data shows that money invested between November and April often performs far better than investments made between May and October.

This so-called six-month effect means that now could be the perfect time to use up your annual Isa allowance if you want to give it the best start.

Number-crunching by investment group Architas reveals that money invested in the FTSE All Share each year between November 1 and April 30 would have grown by 167 per cent over the past 22 years.

Data shows that money invested between November and April often performs far better than investments made between May and October

Cash invested during these six months would have delivered an average return of 8.4 per cent a year over that period, compared to just 1.3 per cent for money invested from May 1 to October 31.

And analysis shows the phenomenon is not just exclusive to the UK.

Stock markets in each of the major investment regions across the world have also delivered stellar returns in the six-month window from November 1.

Indeed, the effect is even more significant in Japan, where markets have returned an average 11.8 per cent a year over the period.

It would have been 11 per cent in Europe. An investment in Japan between May 1 and October 31 would have lost you money.

Tom Becket, chief investment officer at Psigma Investment Management, says: 'Equity markets tend to have their strongest period in the final few months of the year as people tinker with their portfolio based on what has happened over the previous 12 months and optimism kicks in for the coming year.'

But because the period over which these returns are generated is six months, it is difficult to attribute this trend to any single factor.

Stock markets tend to be quieter across the summer months when much of the City has traditionally been on holiday.

Christmas, meanwhile, has typically been a strong period for the stock market, and investors using up their Isa allowances in March may spark a flurry of activity which spurs on performance too.

Number-crunching by investment group Architas reveals money invested in the FTSE All Share each year between November 1 and April 30 would have grown by 167% over the past 22 years

Adrian Lowcock, investment director at Architas, says: 'Whatever the cause, the six-month effect does seem to exist.

'And, while it's probably not a good idea to go to extremes and take your money out of the stock market for six months of the year, the start of November may be a good time to make new investments.'

But the six-month effect does not materialise every year.

Examples when it has not include 1999 and 2000 around the time of the dotcom bubble, in 2003 ahead of the US invasion of Iraq, and amid the financial crisis in 2008 and 2009.

Will it materialise in 2017? Becket is cautious: 'There is a lot of uncertainty as interest rates start to rise and central banks start to taper quantitative easing.'

But Lowcock is more optimistic on the outlook. He says: 'The global economy looks healthy, the US in particular is growing faster than expected and corporate earnings are growing. However, the UK looks more vulnerable.

'Brexit negotiations and political scandals have the potential to send a curve ball into markets.'

Investors should, of course, be cautious of basing investment decisions around an adage which may be more coincidence than fact.

Another common saying is that investors should 'sell in May and go away' –meaning get out of the stock market in May until the St Leger Day racing fixture in September to boost returns.

The idea is that the summer tends to see fewer gains on the stock market and a greater likelihood of violent swings. Yet analysis from Fidelity found that those who had done so would have lost out in 18 of the past 30 years.

Becket says: 'While it's true that the stock market tends to be quieter over the summer and see its strongest gains at the end of the year, if you base an investment strategy on these sayings you will probably end up looking stupid.'