Principles of Portfolio Construction and the Role of Asset Allocation

Updated for the 2026-2027 CFA® Level I curriculum.

Portfolio construction is the bridge between an investor's investment policy statement and an actual portfolio of assets. Level I tests whether you understand the order of decisions: objectives first, then allocation, then implementation, then monitoring. Questions often present an IPS or a set of constraints and ask you to identify the next correct step or spot a step taken out of order.

Key Takeaways About Principles of Portfolio Construction and the Role of Asset Allocation

• Portfolio construction always starts with the IPS, not with security selection.

• Strategic asset allocation sets long-term target weights across asset classes based on the investor's objectives and constraints.

• Diversification and risk budgeting control how risk is spread across and within asset classes.

• Implementation choices, such as active versus passive vehicles, affect cost and expected tracking error.

• Monitoring and rebalancing keep the portfolio aligned with the strategic targets as markets move.

• Constraints and costs limit which allocations and implementation choices are practical.

What You Need to Know for CFA Level I

• Know the correct order of the portfolio construction process: IPS review, strategic asset allocation, diversification, implementation, monitoring.

• Be able to explain why strategic asset allocation is set before individual securities are chosen.

• Understand risk budgeting as allocating risk, not just capital, across positions.

• Distinguish portfolio implementation choices, such as active management, passive management, and derivatives overlays.

• Recognize that rebalancing exists to control drift from target weights, not to chase performance.

• Identify how liquidity, tax, legal, and time horizon constraints shape both allocation and implementation.

What Is Portfolio Construction?

Portfolio construction is the set of decisions that convert an investor's goals into a specific, holdable portfolio. It sits inside the broader portfolio management process, after planning and before ongoing execution. Planning produces the IPS. Construction uses that IPS to build the portfolio. Execution and feedback then monitor and adjust it.

This note focuses on construction itself: how allocation decisions get made, how risk gets spread across the portfolio, and how the portfolio gets implemented and kept on track. Asset class selection and asset allocation mechanics are covered on a separate note. Here, asset allocation is treated as the central input that construction relies on, not as a topic to define from scratch.

Translating the IPS Into a Portfolio

The IPS states return objectives, risk objectives, and constraints such as liquidity needs, time horizon, tax status, legal restrictions, and unique circumstances. Portfolio construction begins by converting these qualitative and quantitative statements into a portfolio structure.

A return objective stated as "8% nominal return" and a risk objective stated as "willing to accept moderate volatility" get translated into a target asset mix that historically has produced a return and volatility profile consistent with those statements. A short time horizon or high liquidity need pushes the mix toward assets that can be sold quickly without a large price concession.

The key exam point: allocation decisions must trace back to something in the IPS. If a question shows an allocation that ignores a stated constraint, that allocation is wrong, regardless of its expected return.

Strategic Asset Allocation

Strategic asset allocation sets long-term target weights for each asset class based on the investor's objectives and constraints, plus capital market expectations. It is called "strategic" because it reflects the investor's long-run position, not short-term market views.

Asset allocation matters more than individual security selection for explaining portfolio-level risk and return over time. This is why Level I treats it as the central decision in construction. Once strategic weights are set, later stages fill in the details, but they do not override the strategic targets without a documented reason tied back to the IPS.

Two general approaches to setting these weights appear in Level I material:

• A top-down approach starts with the overall allocation across asset classes, then narrows to sectors, then securities.

• A bottom-up approach starts by identifying attractive securities, then builds the allocation up from those choices.

Most portfolio construction approaches used in practice, and tested at Level I, favor top-down sequencing because it keeps the allocation aligned with the IPS from the start.

Diversification and Risk Budgeting

Diversification spreads investments across assets whose returns do not move together perfectly, reducing portfolio-level risk without giving up expected return. Risk budgeting takes this further by explicitly allocating a risk limit, not just a capital amount, to each asset class, strategy, or manager.

A capital-weighted view can be misleading. A 10% allocation to a highly volatile asset class can contribute far more than 10% of total portfolio risk. Risk budgeting asks: given the allocation, how much of the portfolio's total risk comes from each piece, and does that match the investor's risk tolerance?

For Level I, know that risk budgeting is a refinement of diversification. It shifts the question from "how is capital spread out" to "how is risk spread out."

Implementation and Security Selection

Once strategic allocation and risk budgets are set, implementation decides how each allocation gets filled. Choices include:

• Active management, where a manager tries to outperform a benchmark within an asset class

• Passive management, using index funds or ETFs to match a benchmark

• Derivative overlays, used to adjust exposure without transacting in the underlying assets directly

Portfolio implementation decisions affect cost, expected tracking error, and speed of execution. Active management typically costs more and introduces the possibility of underperforming the benchmark. Passive management costs less but gives up the chance to beat the benchmark. These trade-offs must fit within the constraints already stated in the IPS.

Monitoring and Rebalancing

Markets move, so actual portfolio weights drift away from strategic targets over time. Monitoring tracks this drift. Rebalancing brings the portfolio back toward target weights, usually based on either a calendar schedule or a percentage-band trigger.

Rebalancing is a discipline, not a market call. It is triggered by drift from the strategic target, not by a view that one asset class will outperform another. A question that describes rebalancing based on a forecast, rather than on drift from target weights, is describing something other than standard rebalancing discipline.

The Role of Constraints and Costs

Constraints from the IPS, liquidity needs, time horizon, tax status, legal and regulatory restrictions, and unique circumstances, limit which strategic weights and implementation choices are realistic. Costs, including trading costs, management fees, and taxes, reduce the portfolio's net return and must be weighed against any expected benefit from a given allocation or implementation choice.

A portfolio construction process that ignores costs will overstate expected performance. A process that ignores constraints may produce a portfolio the investor cannot legally hold or cannot access when cash is needed.

The Portfolio Construction Process Framework

The table below summarizes the sequence tested at Level I.

Worked Example

Scenario: Priya manages a portfolio for a client with a 15-year time horizon, a stated need for $40,000 in liquid assets within the next 12 months, and a moderate risk tolerance documented in the IPS. Capital market expectations suggest equities will outperform bonds over the next decade, but with higher volatility.

Step 1: Review the IPS

The moderate risk tolerance and 15-year horizon support meaningful equity exposure. The 12-month liquidity need means part of the portfolio must stay in cash or near-cash instruments regardless of long-term return expectations.

Step 2: Set strategic asset allocation

Priya sets target weights of 55% equities, 35% fixed income, and 10% cash and equivalents. The cash allocation is sized to cover the liquidity need with a buffer.

Step 3: Apply diversification and risk budgeting

Within equities, Priya checks that no single sector or region dominates the risk contribution. She confirms that despite equities being 55% of capital, they do not represent an outsized share of total portfolio risk beyond what the IPS risk tolerance allows.

Step 4: Implement

Priya uses passive index funds for the core equity and bond allocations to control cost, with a small active allocation in a less efficient market segment where she has research support.

Step 5: Monitor and rebalance

Priya sets a rebalancing band of plus or minus 5% around each target weight. If equities rise to 62% of the portfolio after a strong market, she rebalances back toward 55%, regardless of her forecast for equities going forward.

Every decision traces back to the IPS. The liquidity need shaped the cash allocation. The risk tolerance shaped the equity-bond split. Rebalancing exists to maintain that split, not to make a new market call.

Common Exam Traps

Starting with securities before objectives

A question may describe a manager picking attractive stocks first, then building an allocation around them. This reverses the correct order. Objectives and constraints come first, then allocation, then security selection.

Treating asset allocation as permanent

Strategic weights are long-term targets, not fixed forever. They get revisited if the IPS changes, but day-to-day management should not abandon them based on short-term forecasts.

Ignoring implementation costs

An allocation that looks optimal before costs can underperform a simpler allocation after fees and taxes. Level I expects you to factor in costs when comparing implementation choices.

Confusing construction with the broader management process

Portfolio construction is one phase within the full portfolio management process. Planning (the IPS) comes before construction. Execution and feedback continue after it. A question about writing the IPS itself is testing planning, not construction.

Practice Question

An investment manager has just finished documenting a client's return objective, risk tolerance, time horizon, and liquidity needs in the IPS. Which of the following is the most appropriate next step in the portfolio construction process?

1. Select individual securities expected to outperform their sector benchmarks

2. Set strategic asset allocation targets based on the documented objectives and constraints

3. Establish a rebalancing schedule based on expected market volatility

FAQs About Principles of Portfolio Construction and the Role of Asset Allocation