The starting point is market value, and not total market value. Indices use free float adjusted capitalisation, removing government holdings, controlling family stakes, cross-shareholdings and anything else not circulating in the market. That adjustment matters enormously in some markets, since large companies in certain economies have substantial portions of their equity held permanently outside the float. A second adjustment covers the proportion available to foreign investors. Where a market caps foreign ownership, or restricts foreign participation in particular sectors, indices weight only the investable portion. A market with large capitalisation and limited openness can therefore carry a weight far below its share of market value.
A third layer is the inclusion factor. Where a market has not yet fully met accessibility standards, providers may include it at a partial rate, for instance at twenty per cent, raising it later as conditions improve. This mechanism allows weight changes to occur in stages and avoids concentrating large capital movements into a single date. Inclusion and exclusion decisions follow a consultation process. Providers publish consultation documents, seek views from market participants, set observation periods, and then announce decisions and effective dates. The transparency of that process is high, and its outcomes have observable effects on capital flows into the markets concerned.
The scale of passive money gives these decisions real force. When a weight rises, funds tracking the index must buy, and the buying concentrates around the effective date. Research shows the affected securities typically move in price between announcement and implementation, and that movement is unrelated to anything happening within the businesses. Concentration of weights is another feature worth examining. Country weights in emerging market indices cluster heavily in a few markets, with the largest several often exceeding seventy per cent of the total.
What is described as emerging market allocation is therefore substantially an allocation to a handful of economies, with the remaining twenty or more sharing a modest residual. Rules differ between providers and so do the results. Two funds both described as emerging markets, tracking indices from different providers, can hold noticeably different country mixes. Which markets are included, at what inclusion factors, and how particular territories are classified are not aligned across providers. One technical detail worth remembering is that weights update on a fixed schedule, usually quarterly or semi-annually.
The distribution an index reflects therefore drifts from the actual distribution between reviews, and the drift is largest during periods of sharp market movement. For investors, the practical response is to examine the actual country and sector breakdown rather than relying on the index name. This information appears in fund documentation and is updated monthly. Identical names covering different content is common in this area, and the differences are large enough to change a portfolio's characteristics. A final observation concerns sector alongside country. Emerging market indices carry sector weights quite different from developed market indices, with financials and technology hardware typically prominent. An allocation intended as geographic diversification therefore carries a sector tilt as well, and the sector effect has sometimes explained more of the return difference than the geographic one did.