Home Bias, Correlation and Concentration — The Concepts
Three concepts help in reading a portfolio that spans countries: home bias, correlation and concentration. This lesson explains each in plain terms, shows how they are measured or recognised, and is clear about what none of them can tell an investor.
Home bias
Home bias is the tendency of investors to hold most of their investments in their own country. It describes a pattern of behaviour. It is not a rule, and it is not a measure of return.
Its consequence is dependence. A person who works in India, owns a home in India and holds only Indian investments has job, home and savings all resting on the same economy.
Correlation
Correlation measures how closely the returns of two investments move together, on a scale from −1 to +1. At +1 they move exactly in step, so holding both gives no smoothing of the portfolio's ups and downs. The further below +1 the correlation is, the more the movements of one can offset the other.
Two cautions apply. Correlation is measured from past data, and it changes over time, so a figure from one period need not hold in the next. And it describes how returns move together, not how large they are: two investments can move in step and both fall.
Concentration
Concentration means a large share of a portfolio in one company, one sector or one country, so that a single setback has a large effect.
Counting countries is not enough to rule it out. On 30 September 2026 the United States was 72.94% of the MSCI World Index, which covers developed markets as a group. A fund tracking a multi-country index can therefore still be concentrated in one country.
What the concepts cannot do
These are tools for describing a portfolio. None of them tells an investor what any market will return, and none of them points to a correct share to hold at home or abroad. Overseas holdings bring market risk and currency risk in both directions, whatever the correlation or the spread across countries.
Rules at a glance
Many countries, one large share
Jatin, 39, a resident in Surat, holds a fund that tracks the MSCI World Index and describes it as spread across the developed world.
On the index weights of 30 September 2026, of every ₹1,00,000 in a fund that held the index exactly, 72.94% × 1,00,000 = ₹72,940 was in US shares and ₹1,00,000 − ₹72,940 = ₹27,060 was in all other developed markets together. The fund spans many countries, but its result depends mostly on one. The weights are a snapshot and change over time.
Correlation at its two extremes
- Take three invented investments over two periods. A returns +10%, then −10%. B does the same, exactly in step with A (correlation +1). C returns −10%, then +10%, exactly opposite to A (correlation −1). The returns are assumptions for the example.
- A portfolio holding half in A and half in B returns 0.5 × 10 + 0.5 × 10 = +10% in the first period and 0.5 × (−10) + 0.5 × (−10) = −10% in the second. It swings exactly as A does.
- A portfolio holding half in A and half in C returns 0.5 × 10 + 0.5 × (−10) = 0% in the first period and 0.5 × (−10) + 0.5 × 10 = 0% in the second. The swings cancel.
Result. At +1, combining two investments gives no smoothing. Below +1 the movements of one offset part of the other's, and at −1 in this example they cancel completely. These are the two ends of the scale, and a measured correlation changes over time.
Key points
- Home bias is the tendency to hold most of one's investments in one's own country; it is a pattern of behaviour, not a rule or a return.
- Correlation measures how closely two investments' returns move together, from −1 to +1; at +1, combining them gives no smoothing.
- Correlation is measured from past data and changes over time.
- Concentration is a large share of a portfolio in one company, sector or country.
- On 30 September 2026 the US was 72.94% of the MSCI World Index, so a multi-country index can still be concentrated.
Common misunderstandings
- Home bias is not a rule or a recommendation: it describes how investors tend to behave.
- A correlation figure is not permanent and not a forecast: it comes from past data and changes over time.
- Holding a fund that covers many countries is not the same as being spread evenly: one country was 72.94% of the MSCI World Index on 30 September 2026.
- Low correlation does not mean low risk: it describes how returns move together, not how far they can fall.
Questions people ask
At what correlation does combining two investments give no smoothing?
At +1, where the two move exactly in step.
Does home bias mean holding nothing abroad?
No. It means holding most of one's investments in one's own country.
Can these concepts tell which market will do better?
No. None of them tells an investor what any market will return.
What this lesson relies on
- MSCI World Index factsheet, 30 September 2026
- MSCI ACWI Index factsheet, 30 September 2026
This lesson was reviewed independently against these sources on 7 October 2026. Rules change: check the current regulation, scheme document or policy wording before relying on any figure. This is education, not advice.