First, the key terms.

Correlation
A measure of co-movement under a particular sample and method.
Concentration
Dependence on a small set of holdings or shared risk drivers.

The idea, explained

A portfolio concentrated in similar businesses can remain exposed to the same economic forces even if it contains many holdings. Diversification can reduce concentration risk, but it does not eliminate market losses. Asset allocation and rebalancing decisions depend on goals, time horizon and ability to absorb losses.

STEP 1

Look for shared causes

Several technology funds may all depend on the same large companies and interest-rate conditions. Counting fund names hides those overlaps. Inspect underlying weights and economic exposures.

STEP 2

Distinguish risk reduction from elimination

Combining imperfectly related exposures can reduce some variability. Broad market shocks can still affect many holdings, and correlations can change during stress. Historical diversification is evidence to assess, not a guarantee.

Follow a worked example.

Two funds may have different names while both hold many of the same large technology companies. Combining them can leave substantial overlap. Looking through to underlying holdings is more informative than counting the number of funds.

Walk it through, one step at a time

  1. A portfolio holds $500 in a company directly and $500 in a fund that allocates 40 percent to that same company.
  2. Total direct-plus-indirect exposure is $500 + $200 = $700, or 70 percent of the $1,000 portfolio.
  3. Two account positions therefore conceal a large single-company concentration.

Where people get stuck

A diversified portfolio can still fall in value. Relationships between assets can also change during stressful periods.

Now try it yourself.

Pause before opening each answer. Explain your reasoning in your own words.

1. Check the core idea

Do ten funds always provide more diversification than two?

Reveal the answer & reasoning

No. Their underlying holdings and risk exposures may overlap. Count the sources of risk, not only the products.

2. Apply what you learned

Does adding another fund always diversify the portfolio?

Reveal the answer & reasoning

No. It may duplicate existing holdings or risk drivers. Evaluate the combined underlying exposures and weights.