The NZX-50 share index cracked the milestone 10,000 mark this afternoon continuing a run of record-breaking highs. At 12.30pm it was trading at 10,032 - up 0.072 for the day.

The 10,000 mark is only symbolic but it was something to celebrate, said Mark Lister, head of research at Craigs Investment Partners.

The NZX-50 is a construct in that it is an index for the country's largest listed companies.

But key numbers often have market sentiment attached to them and this is a big one.

"Fundamentally, it doesn't mean anything," Lister said.

"But people do follow these numbers. We'll get excited if Wall Street's Dow Jones (Index) goes through 20,000, we'll get excited if the S&P 500 goes through 3000. So I don't see why we shouldn't celebrate this."

If nothing else, the indexes lift into five digit territory serves as another reminder of the New Zealand sharemarket's remarkable run in the past decade.

In fact, the NZX-50 has now risen almost 300 per cent since the last low point - a decade ago in February 2009.

The NZX-50 returns are calculated on a gross index basis - with dividends factored in.

If you just looked at the capital return that would be more like 30 per cent up on the last peak in 2007, Lister noted.

However it had still been a "stellar run" for investors and KiwiSavers, he said.

The index had doubled from the 5000 point mark in almost exactly five years - representing annual returns of close to 14 per cent.

The strong bull run appeared to be at an end late last year. Global markets tumbled by almost 20 per cent between October and December - just shy of what investment analysts would have called a bear market.

However a reversal of central bank policy on interest rates - initially in the US - has seen money pour back into equity markets this year as investors seek better returns.

Some big equity fund managers have expressed nervousness about the heady heights the market is now reaching and the valuations of some companies.

It was important not to take annual returns in the double digits for granted, Lister said.

It needed to be acknowledged that this was a golden period.

"Thirteen or 14 per cent returns is not normal, it's exceptional. Over the long run the average is more like seven per cent. So don't get too comfortable and assume the next five or 10 years will go the same way because I strongly suspect they won't."

However, the strength of the sharemarket was also an indication of an economy which was still performing well despite the lack of confidence in some quarters, he said.

"We've got a lot of great businesses on our market now and it's a much more diverse market than it was five to 10 years ago, with more interesting companies doing interesting things offshore. I think it's something we should celebrate."

Locally, a combination of low inflation data - which now points to Reserve Bank interest rate cuts - and the Government's backdown on the Capital Gains Tax (which would have hit company valuations) seemed to have given the NZX another boost in the past week, Lister said.