Deloitte's partner Paul Munro said South Island listed companies had "bucked the traditional seasonal winter slowdown period", taking the index to its highest point since starting in 2008.
Munro said the South Island was leading the way in steering the country out of tough economic times.
"The resilience that South Island companies have shown over recent years, in adverse economic conditions, is remarkable," he said.
"That strength underpins the performance over the past 12 months across a number of sectors resulting in investors scrambling for shares in established companies like Ryman Healthcare, Kathmandu and Skyline Enterprises."
Twenty-one of the 31 companies grew during the year, led by Ryman Healthcare with a $1,455 million, or 84.1 per cent, increase in market capitalisation.
Ebos Group held the second ranked position on the index, gaining $232.7 million (58.7 per cent) and Kathmandu grew by $252.5 million (99.4 per cent).
The biggest fall came from mining company Bathurst Resources - down $263.9 million (74.4 per cent) in the year - which is locked in litigation over its plans to mine the West Coast's Denniston Plateau.
Other companies to suffer in the year were Silver Fern Farms and NZ Windfarms, which fell $35.1 million and $23.9 million respectively.
Of the various sectors, energy and mining was the only one to lose market capitalisation and bio-technology had the best performance. Munro said the sector's growth was largely due to the more than 200 per cent gain by Pacific Edge.
No other major index had achieved the same results as the Deloitte South Island Index since its inception, Munro said.
"The investments in the Christchurch rebuild and the resilience of the South Island's primary sector continue to underpin the performance of the wider South Island economy, creating a solid platform for continued growth," he said.
Munro predicted continued growth in the index as the rebuild "finally kicked off" and as the US followed through with its signalled end to quantitative easing measures.
Both Synlait Milk and Meridian Energy would add significant value to the index with their listings this year, he added.
Deloitte's annual review of the quarterly Index report was presented at a function in Christchurch today attended by Finance Minister Bill English and South Island business leaders.