The Deloitte South Island index of listed companies' market capitalisation grew 8.8%, or $2.1billion, to hit $26.9billion for the quarter to September.
More than $20billion of the total $26billion was credited to just four companies of the total 31 - Meridian Energy rose 5.3% to $8.41billion, Ryman Healthcare was up 17% to $7billion, EBOS Group rose 25% to $3.42billion and Synlait Milk, was down 5.2% to $1.94billion.
Market capitalisation is the price of all ordinary shares on issue, while the index itself is based on listed companies of the NZX and Unlisted markets with extensive South Island interests.
Seventeen of the 31 companies notched up growth for the quarter.
Queenstown-founded tourism operator Skyline Enterprises slipped from the $1billion record it hit in the past quarter, down 4.3% to $977million capitalisation, while also in that band, Heartland Bank rose 2.7% to $978million.
Deloitte corporate finance partner Scott McClay said the top four companies, Ryman Healthcare, Meridian, EBOS and Synlait Milk, continued to provide the index with "significant weight".
"These four companies, each with market capitalisations in excess of $1billion, collectively grow 10.8% in market capitalisation.
"It was particularly pleasing to see the next tier of companies in the index also continuing to perform in the quarter," Mr McClay said in a statement.
Mr McClay said Synlait's "golden run" paused during the September quarter when it posted the largest decline, in dollar terms, falling $105.7million.
The Deloitte index recorded growth of $2.19billion, or 8.8%, following a subdued first quarter and strong second quarter of 2018.
Outside the top four, Mr McClay said the index's best performers, in percentage terms, were Energy Mad, whose market capitalisation increased 114.3%, or $1.6million, followed by Dunedin-based Blis Technologies which increased its market capitalisation by 38.2%, or by $5.5million.
The most significant percentage declines were SeaDragon, which dropped 33.3%, or $4.5million, Smiths City Group fell by 22.9%, or $4.7million and Dunedin's Scott Technology dropped 12.6%, or $33.4million.
The smallest 10 companies collectively grew, recording a $2.1million, or 2.3%, increase in market capitalisation.
Index gains progress were seen in five of the seven sectors, the largest being 20.3% in the manufacturing and distribution sector, while the primary sector recorded the largest decline, falling 1.6%.
