The S&P/NZX 20 Index can be seen as the “big brother” to the New Zealand equity market’s flagship S&P/NZX 50 Index. Both indices are from the same DNA with a similar objective: to measure New Zealand’s investable capital market.
Yet with fewer constituents, the S&P/NZX 20 Index offers more distinctive size, liquidity and trading characteristics that are ideal for index-linked investment products and exchange-traded derivative contracts.
The S&P/NZX 50 Index is seen as New Zealand’s pre-eminent market benchmark, used by a large number of mutual funds, KiwiSaver and exchange-traded funds. It covers the vast majority of New Zealand’s listed capital market at 97.7%, however it can include some smaller, less liquid companies.
Typically, broad market indices and flagship benchmarks aim for an 80%-85% coverage of total stock market capitalization to best reflect the capital market while providing broad market representation, as well as investability and liquidity.
The S&P/NZX 20 Index covers approximately 83% of the S&P/NZX All Share Index, which means the index is composed of larger, more liquid companies, with an average constituent market capitalization of more than double the S&P/NZX 50 Index.

Furthermore, market dynamics over the past 10 years have seen more concentration of market capitalization move into the top 20 stocks. This has resulted in the S&P/NZX 20 Index’s coverage of the S&P/NZX 50 Index to increase from 74% to 84% since June 2015.