## **Learning Outcomes**

This article explains the role of passive and enhanced indexing within portfolio management, clarifying how they differ in objectives, implementation techniques, and expected tracking error. It details how ESG considerations and client-specific requirements are translated into index rules, including security selection, weighting schemes, and rebalancing methodologies. The article examines when investors might prefer pure passive replication versus enhanced strategies that incorporate factor tilts, tax optimization, or selective ESG overlays while remaining benchmark-aware. It outlines how ESG indexes and fully custom benchmarks are designed, documented, and maintained, and how these choices affect investability, costs, and benchmark risk. The article analyzes common sources of tracking error in ESG and bespoke indexes, highlighting the implications for risk budgeting, performance attribution, and manager evaluation in a CFA Level 3 context. It reviews practical limitations such as data quality, methodology subjectivity, liquidity constraints, and regulatory considerations, enabling focused preparation for item set questions that test the construction, selection, and critical assessment of ESG and custom benchmarks relative to standard market-capitalization indexes.

## **CFA Level 3 Syllabus**

For the CFA Level 3 exam, you are expected to understand the differences between pure passive and enhanced indexing, the considerations involved in constructing custom indexes (including ESG-related benchmarks), and how these indexes impact portfolio management and performance measurement, with a focus on the following syllabus points:

- Explain the principles, implementation, and tracking challenges of passive and enhanced indexing strategies.
- Discuss the use of ESG factors and client-driven customization in index selection and construction.
- Assess the risks and limitations of ESG/custom indices for institutional portfolios.
- Evaluate index construction rules, benchmarking pitfalls, and index suitability.
- Compare tracking error considerations in traditional, enhanced, ESG, and bespoke indexes.

## **Test Your Knowledge**

_Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision._

1. What is the main objective of passive indexing, and how does enhanced indexing differ?
2. List two advantages and two limitations of using ESG indexes as portfolio benchmarks.
3. In what situations might an investor require a custom or client-driven index for benchmarking?
4. What risks may arise if a custom ESG index is poorly constructed or lacks transparency?

## **Introduction**

Passive and enhanced indexing are central tools for portfolio managers aiming to balance cost, risk, and tracking error. As investor demand grows for ESG-aligned benchmarks and strategies tailored to specific objectives or constraints, index providers and clients increasingly collaborate to produce custom indexes. Understanding how ESG and bespoke indexes are constructed, maintained, and used in practice is tested at CFA Level 3 and is essential for portfolio construction and evaluation.

> **Key Term: passive indexing**
> A portfolio management approach that replicates a published benchmark or index, aiming to match its return and risk characteristics with minimal active input.
>
> **Key Term: enhanced indexing**
> A rules-based or semi-passive portfolio approach aiming to reduce tracking error or slightly outperform a benchmark by minor deviations, typically using predictive signals, factor tilts, or cost minimization.
>
> **Key Term: ESG index**
> An index constructed to reflect environmental, social, and governance (ESG) factors in its security selection or weighting methodologies.
>
> **Key Term: custom index**
> An index created or modified for a specific client's needs, often integrating unique constraints, tilts, or factor exposures beyond standard benchmarks.
>
> **Key Term: tracking error**
> The standard deviation of the active (excess) return of a portfolio relative to its benchmark, used to measure index replication accuracy or the risk of deviation from the specified benchmark.

## **Passive Versus Enhanced Indexing: Foundations**

Passive indexing seeks to mimic a specified benchmark (e.g. S&P 500, FTSE All-World). The portfolio manager buys securities according to the published methodology, aiming for minimal trading, low costs, and near-zero tracking error. Enhanced indexing maintains the focus on close benchmark tracking but allows for limited tactics—usually systematic, such as factor tilting, tax management, or minimizing known trading costs.

> **Key Term: benchmark**
> A standard portfolio or index against which the returns and risk of a portfolio are measured for evaluation and performance attribution purposes.

### Passive Indexing

Managers using traditional passive indexing:

- Fully or partially replicate index constituents (via full replication, stratified sampling, or optimization).
- Accept benchmark returns net of fees and trading frictions.
- Use reconstitution and rebalancing rules tied to the public index provider.

Passive strategies strictly follow the published rules and weights, limiting judgment and often reducing costs and turnover.

### Enhanced Indexing

Enhanced strategies maintain benchmark risk exposure but seek incremental improvements:

- Optimize weights for lower tax drag, lower trading costs, or slight factor exposures while constraining tracking error.
- Use systematic methods (e.g., factor scoring, sampling, or slight tilts).
- May implement minor ESG exclusions or overweights within a tracking error budget.
- Typically suitable for large institutional mandates or ETFs with capacity to support custom but scalable rules.

Enhanced indexing delivers risk and return profiles tightly coupled to the index but may outperform by a narrow margin (typically zero to 1% per annum) or reduce relative value at risk.

> **Key Term: index construction**
> The process of selecting constituents, assigning weights, and defining rebalancing rules to create an investable reference portfolio.

## **ESG Indexes and Custom Benchmarks**

### ESG Indexes

ESG indexes integrate sustainability or ethical considerations into index rules. This may be achieved by:

- Excluding securities or sectors based on ESG screens (exclusionary).
- Weighting securities using ESG ratings or scores (tilting/positive screening).
- Integrating thematic priorities (e.g., climate, diversity) or engagement targets.
- Prescribing minimum ESG ratings for inclusion, or applying best-in-class selection.
- Constructing lower-carbon or net-zero transition versions of broad indexes.

Managers and clients may use ESG indexes as standalone benchmarks or as constraints/factored overlays on traditional mandates.

> **Key Term: ESG screening**
> The process of including or excluding securities based on environmental, social, and governance criteria, often per explicit client or regulatory requirements.

### Custom (Client-Driven) Indexes

A custom index is constructed to reflect a specific client’s objectives, constraints, or regulatory concerns. Features might include:

- Incorporation of client-specific exclusions (e.g., faith-based, regulatory, or investment policy requirements).
- Alignment with non-standard risk or liability measures (e.g., alternative duration targets for defined benefit funds).
- Risk budget overlays, non-cap weighting methodologies, or strategic factor tilts.
- Specific currency/exposure constraints or unique geographic or sector allocations.

> **Key Term: index methodology**
> The publicly documented set of rules governing index constituent selection, weighting, and maintenance, ensuring transparency and replicability.

## **Construction and Implementation Considerations**

### Index Selection and Construction

When constructing an ESG or custom index, key steps include:

- Defining investable universe and rules for inclusion/exclusion.
- Documenting ESG scoring or policy exclusions.
- Selecting weighting methodology (market-cap, equal, factor, ESG-tilt).
- Establishing rebalancing, review, and reconstitution timing and mechanisms.
- Validating data sources: ESG data, corporate actions, and coverage.

Managers must consider index investability, capacity, turnover, and cost implications.

### Tracking Error and Benchmark Risk

Any deviation from a standard index (ESG, factor, or client constraint) increases expected tracking error. The impact is sensitive to:

- Breadth/depth of exclusions or tilts: removing large sectors or high-weighted securities increases tracking error.
- Frequency and volatility of rebalancing: more frequent or event-driven rebalancing raises turnover and relative risk.
- Data and rating disagreement (especially for ESG metrics).

### **Worked Example 1.1**

A pension fund wishes to implement a custom ESG index excluding all fossil fuel companies and overweighting companies rated AA or better by a chosen ESG rating agency. The fund is benchmarked traditionally to the MSCI World.

> **Answer:**
>
> - The manager defines the custom index parameters: all MSCI World constituents except fossil fuel companies, with index weights increased for securities rated at least AA (e.g., +30% over market-weight).
> - The custom index is reconstituted quarterly, using updated ESG ratings.
> - The expected tracking error will exceed that of a broad ESG index unless the fossil fuel sector and overweighted stocks are minor components, in which case tracking error may remain low. The client’s risk policy and reporting must reflect these potential deviations.

## **Risks, Limitations, and Practical Challenges**

### Limitations

- Subjectivity: Custom index methodologies and ESG scoring lack cross-provider standardization.
- Data Gaps: Incomplete or inconsistent ESG data undermines replicability.
- Higher Tracking Error: Index modifications may produce larger, unpredictable deviations—particularly in crisis periods or if constraints create unintentional factor or sector exposures.
- Liquidity and Cost: More exclusions may increase turnover, impact transaction costs, and reduce investability for large mandates.
- Regulatory: Some ESG or custom indexes may not count as “recognized” benchmarks for certain legal or reporting purposes.

### **Worked Example 1.2**

An asset owner commissions a low-carbon index for a European equity allocation, excluding coal and tobacco, with periodic input from its internal ESG committee.

**Question:** What are potential portfolio management concerns for performance attribution and reporting?

> **Answer:**
>
> - The deviation from a market-cap index will increase tracking error.
> - Performance attribution must distinguish performance driven by systematic factor exposures, sector tilts, and ESG screens.
> - Benchmark reporting for stakeholders/investment committee must clarify these sources of relative return, especially if returns diverge in periods with sector or regional ESG-driven dispersion.

### **Exam Warning**

> Using an ESG or custom benchmark does not guarantee improved risk-adjusted returns. Deviations from standard indexes may increase tracking error, limit investability, or introduce biases. In the exam, be careful to distinguish between “beta capture” (passive exposure) and “risk of unintended active exposures” in custom or ESG benchmarks.

### **Revision Tip**

> While ESG and custom indexes are accepted for benchmarking, CFA candidates should memorize the key differences in construction, transparency, replicability, and tracking error implications—especially when evaluating manager skill and benchmarking suitability.

## **Summary**

Passive and enhanced indexing strategies form the backbone of many institutional and ETF portfolios. ESG and custom indexes modify core benchmarks to address client values, policy goals, and compliance needs. These modifications can increase tracking error, must be systematically documented, and often raise implementation and evaluation complexities. Candidates should understand construction rules, transparency requirements, risks introduced, and the impact on portfolio tracking and performance attribution.

## **Key Point Checklist**

_This article has covered the following key knowledge points:_

- Define and contrast passive and enhanced indexing, focusing on index construction and tracking error.
- Outline ESG index design and typical approaches to integrating ESG factors and policies.
- Explain the rationale and methodology for custom/client-driven indexes, including examples.
- Discuss risks, limitations, and tracking error impacts of ESG and custom indexes.
- Highlight portfolio management and CFA exam considerations when using non-standard benchmarks.

## **Key Terms and Concepts**

- passive indexing
- enhanced indexing
- ESG index
- custom index
- tracking error
- benchmark
- index construction
- ESG screening
- index methodology

Passive and enhanced indexing - ESG and custom indexes