Portfolio construction

Asset allocation

Asset allocation is the division of a portfolio among asset classes, such as stocks, bonds and cash, expressed as percentages of the portfolio’s total value.

What it means

A portfolio’s asset mix describes how much of its value sits in broad categories such as stocks, bonds and cash. Each category has different risks, so the mix helps describe what the portfolio is exposed to. A target allocation is the mix an investor intends to maintain; the current allocation is what the holdings are worth now. Market movements and transactions can make the two differ.

Asset allocation is broader than choosing individual stocks. A portfolio that holds shares of ten companies may be diversified across those companies but still be allocated entirely to stocks. Likewise, spreading stock holdings across sectors or countries changes stock exposure, not the share of the portfolio held in bonds or cash. The categories must be defined consistently: for example, an exchange-traded fund belongs in the relevant asset category rather than automatically counting as a separate asset class.

How it is calculated

Asset-class weight (%) = (current value of holdings in the asset class / current total portfolio value) × 100

  • Asset-class weight is the percentage of the portfolio assigned to one category.
  • Current value of holdings in the asset class is the sum of the current market values of positions assigned to that category, measured in US$ in this example. Cash is counted at its cash balance.
  • Current total portfolio value is the value of all included holdings plus cash, measured in the same currency and at the same valuation time.

Calculate a weight for each category. The weights should add to 100%, apart from rounding, when every holding is included and categories do not overlap. If the portfolio includes borrowing or short positions, specify whether weights use net portfolio value or gross exposure; otherwise, a simple percentage breakdown can be misleading.

Worked example

Suppose a hypothetical portfolio contains US$6,000 in stocks, US$3,000 in bonds and US$1,000 in cash. Assume these are current values and there are no other positions.

  1. Add the values: US$6,000 + US$3,000 + US$1,000 = US$10,000 total.
  2. Calculate the stock weight: US$6,000 / US$10,000 × 100 = 60%.
  3. Calculate the bond weight: US$3,000 / US$10,000 × 100 = 30%.
  4. Calculate the cash weight: US$1,000 / US$10,000 × 100 = 10%.

The hypothetical allocation is therefore 60% stocks, 30% bonds and 10% cash. If stock prices change, the percentages change even without a trade. A US$1,000 stock purchase funded entirely from the cash shown would leave US$7,000 in stocks, US$3,000 in bonds and no cash: 70%, 30% and 0%, respectively, assuming no price changes or transaction costs.

Why it matters before you trade

A proposed transaction can change the portfolio’s mix, even when the order looks small on its own. Checking the expected weights before placing an order makes the effect visible. The calculation should account for both sides of a transaction: buying a stock with cash increases stock exposure and reduces cash; selling a stock for cash does the reverse, before costs and subsequent price changes.

The mix also does not capture every risk. Two portfolios can both be 60% stocks yet differ substantially in sector, country, currency, company-size and single-position exposure. Allocation percentages describe where value is held, not how much the portfolio could lose or what return it will earn.

How PreTrAIde uses it

PreTrAIde is a stock pre-trade analysis platform. For a user-built stock basket, it provides portfolio breakdowns by country, sector, region, currency and market capitalization, along with a Herfindahl-Hirschman concentration index. Those breakdowns describe the basket’s stock exposures; they are not a full stocks-versus-bonds-versus-cash allocation for an entire portfolio.

PreTrAIde returns a GO, NO-GO or MODIFY verdict for the basket and each line, with a model-estimated success probability, risk assessment, suggested execution strategy and plain-language reasoning. These outputs are decision support, not investment recommendations. Users place any trades themselves through their own broker.

Common mistakes

  • Treating stock diversification as asset-class diversification. Several stock positions still belong to the stock category.
  • Using purchase prices instead of current values. Weights based on old costs may not describe today’s allocation.
  • Mixing denominators. A stock’s share of a proposed basket is not necessarily its share of the entire portfolio.
  • Double-counting funds. Decide whether to classify a fund as one holding or look through to its underlying assets, and apply that approach consistently.
  • Ignoring cash used or received. A transaction changes both the traded asset and the funding or proceeds category.

Frequently asked questions

What is the difference between asset allocation and diversification?

Asset allocation describes the proportions held in asset classes such as stocks, bonds and cash. Diversification describes how exposure is spread; it can be assessed across asset classes and within a class, such as across individual stocks.

How do you calculate asset allocation percentages?

Divide the current value of each asset class by the current total portfolio value, then multiply by 100. Use the same valuation time and currency for every category, and include cash.

Can asset allocation change without trading?

Yes. Changes in the market values of holdings can alter their portfolio weights even when the number of shares held stays the same.

Related terms

Diversification Diversification is the practice of spreading a portfolio across holdings with different sources of risk so that its outcome depends less on any single holding. Portfolio rebalancing Portfolio rebalancing is adjusting holdings to bring a portfolio’s current weights closer to chosen target weights after prices or circumstances change. Portfolio concentration Portfolio concentration is the extent to which a portfolio’s value depends on a small number of holdings or on shared exposures such as a sector or country. Sector exposure Sector exposure is the share of a portfolio’s value allocated to companies in a particular industry sector, usually expressed as a percentage. Position sizing Position sizing is the process of deciding how many shares to hold or trade based on available capital, intended portfolio weight and the amount of risk an investor is prepared to take. Pre-trade analysis Pre-trade analysis is the assessment of a proposed stock order or basket before placement, estimating execution costs, liquidity and risk to inform the investor’s decision and execution approach.

Portfolio construction

Herfindahl-Hirschman index (HHI) Effective number of stocks Country exposure Market capitalization Large-cap stocks Mid-cap stocks Small-cap stocks Exchange-traded fund (ETF) All glossary terms →

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Educational content, not investment advice. PreTrAIde is analysis software, not a broker: it never executes orders, and its verdicts are decision support, not recommendations to buy or sell.