Withers said initial uncertainty over the future of the Tiwai Aluminium smelter's power contract and the threat of a Labour Greens alternative power policy had weighed on the stock.
She told the meeting that the price reflected the market's view, but at times there appeared to be clear disconnect between the company's share price and its performance.
Mighty River's debut on the NZX also coincided with a turning point for bond yields, which had affected Mighty River and other utility stocks around the world.
The company's poor showing on the market was despite a strong financial showing in the year just past.
Mighty River's net profit was $114.8 million in the year ended June 30, up from $67.7m a year earlier and well ahead of its prospectus in April when it forecast a profit of $94.8m.
At today's meeting, the company said it expects to meet its prospectus forecast earnings before interest, tax, depreciation, amortisation and fair value adjustments of $498 million in the year ending June 30, 2014, and anticipates paying a first-half dividend of 5.2 cents per share.
The power company lifted net profit guidance $35 million to $195 million due to changes in the value of its financial instruments and cheaper than expected interest costs.
The Government sold 49 per cent of Mighty River Power in a share float in May as part of its so called mixed ownership model of partial privatisations that will include the smallest of the state's generators, Genesis, next year.
Mighty River produces 17 per cent of New Zealand's power -- 90 per cent of it coming from renewable hydro and geothermal sources.
Withers said Mighty River now had a good ownership mix with a diverse share register including a large retail shareholding base of 28 per cent alongside New Zealand institutions with 10 per cent.
Offshore investors comprise around 10 per cent and the Government has remaining cornerstone holding of around 52 per cent.