Implementation
At the simplest, an index fund is implemented by purchasing securities in the same proportion as in the stock market index. It can also be achieved by sampling (e.g. buying stocks of each kind and sector in the index but not necessarily some of each individual stock), and there are sophisticated versions of sampling (e.g. those that seek to buy those particular shares that have the best chance of good performance).
Investment funds run by Investment managers who closely mirror the index in their managed portfolios and offer little "added value" as managers whilst charging fees for active management are called 'closet trackers'; that is they do not in truth actively manage the fund but furtively mirror the index.
Collective investment schemes that employ passive investment strategies to track the performance of a stock market index, are known as index funds. Exchange-traded funds are never actively managed and often track a specific market or commodity indices.
Globally diversified portfolios of index funds are used by investment advisors who invest passively for their clients based on the principle that underperforming markets will be balanced by other markets that outperform. A Loring Ward report in Advisor Perspectives showed how international diversification worked over the 10-year period from 2000–2010, with the Morgan Stanley Capital Index for emerging markets generating ten-year returns of 154 percent balancing the blue-chip S&P 500 index, which lost 9.1 percent over the same period – a historically rare event. The report noted that passive portfolios diversified in international asset classes generate more stable returns, particularly if rebalanced regularly.
There is room for dialog about whether index funds are one example of or the only example of passive management.
Read more about this topic: Passive Management