Infrastructure company Chorus is 2014's best-performing stock on the NZX 50 gross index, giving shareholders returns of almost 85 per cent over the year.

Almost 30 per cent of its gains followed a draft decision from the Commerce Commission last month on how much the Wellington-based lines company could charge internet retailers for access to its copper lines.

The draft price, which won't be finalised until later this year, was higher than what Chorus is presently allowed to charge under an earlier decision from the regulator.

Chorus last month said the new pricing, if enacted, would reduce its annual earnings by $80 million.

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While this appears to be nothing to celebrate, it is less than half the $170 million the company said would come off its annual earnings under the present pricing regime. Chorus shares hit a 14-month high on the back of the news.

Chorus owns the country's copper-wire phone network and is also building the bulk of the Government's ultra-fast broadband scheme.

Three companies involved in the Government's state asset sale programme were also among the top five best performers last year.

Mighty River Power, after its shares sank 23 per cent below its listing price last January, gave returns of 42.24 per cent in the year.

The electricity company's share price hit a high of $3.10 in December, after National returned to power and the spectre of regulation in the market vanished.

Meridian Energy shares also rallied after National's September 20 election win and the stock was the second top performer, offering returns of 71.75 per cent.

Air New Zealand came in at number four, with returns of 57.94 per cent.

After taking a pounding in 2013, shares in Diligent Board Member Services bounced back last year, offering returns of 38.42 per cent.

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Although the firm, which provides cloud-based software used by directors to access documents, has been plagued by reporting issues, analysts see all that being behind the company.

"The company continues to generate solid free cash flow, has no debt, and benefits in translational terms from a weaker New Zealand dollar," said Rickey Ward, New Zealand equities manager at JBWere.

In November, Diligent lifted its full-year revenue guidance to between US$82.5 million ($106.6 million) and US$83 million, which would be an increase of up to 28 per cent on the previous year. Net income for the nine months to September 30 rose more than 30 per cent to US$6.9 million from the same period of 2013.

Fisher & Paykel Healthcare also ranked among the best-performing stocks, with returns of 62.34 for the year. This followed the company posting record financial results and in December analysts saw it being well positioned with growth options and earnings momentum.

Investors also appear to be buying the story of Spark's metamorphosis, with returns of 35.14 per cent.

The company changed its name from Telecom in August, as a "marker" that its future was different from its past. Spark is part-way through its transformation from being an infrastructure company to a "digital services provider". So far that has seen it launch products like Lightbox, an online television service.

In October Spark briefly reclaimed the top spot as the most valuable company on the NZX.