It comprises the 50 biggest stocks by free-float market capitalisation trading on the New Zealand Stock Market (NZSX).
The calculation of the free-float capitalisation excludes blocks of shares greater than 20% and blocks between 5% and 20% that are considered strategic.
It was renamed the NZX 50 Index in late 2005.
[3] In 2015, the index was renamed to S&P/NZX 50 Index reflecting a 'strategic partnership' between NZX and S&P Dow Jones Indices (S&P DJI).
As part of the partnership, S&P DJI has assumed responsibility for calculating, publishing distributing all NZX indices.