Performance Evidence: Meta-Studies, Tracking Error and Sector Bets of ESG Indices, Costs and Climate Risk as Financial Risk

What you will learn

• What the two best-known meta-studies found and the limits of what they can tell you.
• How to decompose the relative return of an ESG index into sector bets and how to calculate tracking error.
• How to put higher fund costs into euros over a long holding period.
• The difference between transition risk and physical risk and why central banks treat climate risk as financial risk.

Explanation

What the meta-studies say. Friede, Busch and Bassen (2015, Journal of Sustainable Finance & Investment) combined about 2,200 studies and found that roughly 90 % reported a non-negative relation between ESG criteria and corporate financial performance. The NYU Stern Center for Sustainable Business and Rockefeller Asset Management (2021) reviewed more than 1,000 studies from 2015 to 2020: 58 % of studies on company performance were positive, while among studies on portfolio performance 59 % showed similar or better risk-adjusted results than conventional approaches and 14 % were negative. Three limits: "non-negative" includes "no effect"; company-level profitability does not automatically become portfolio return, because prices may already reflect it; and periods matter, since a 2010–2019 window captures a decade when technology beat energy, which helps most ESG portfolios regardless of any "ESG effect". Read the evidence as: no systematic penalty demonstrated, no reliable premium demonstrated either.

Sector bets. ESG and SRI indices (lesson 4) differ from their parent mostly through sector weights: typically underweight energy, materials and utilities, overweight technology, healthcare and financials. The relative return from a sector bet is approximately the active weight (index weight minus parent weight, in percentage points) times the sector's return relative to the rest. This explains most short-term "ESG outperformance" headlines.

Tracking error is the annualised standard deviation of the difference between the ESG index's return and its parent's. At 1 %, the ESG index ends within ±1 percentage point of the parent in roughly two years out of three. Light screens produce tracking errors around 0.5–1.5 %; strict SRI or Paris-aligned indices can reach 2–4 % or more. It tells you how far from "the market" you can land in any single year, in either direction.

Costs. ESG ETFs often carry a slightly higher total expense ratio (TER) than the cheapest conventional ETF on the parent index, because of data licences and smaller fund sizes. Small per year, but it compounds (mechanics in the course "ETFs, Funds & Long-Term Investing").

Climate risk as financial risk. Supervisors distinguish transition risk (losses from policy, technology and preference shifts towards a low-carbon economy: carbon prices, stranded reserves, combustion-engine bans) and physical risk (acute events such as floods, chronic shifts such as heat and sea level). The Network for Greening the Financial System (NGFS), a group of central banks and supervisors, publishes scenarios for both, and the ECB ran a climate stress test for euro-area banks in 2022. For an investor, climate exposure is a risk factor to measure and size whatever your values: fossil producers carry transition risk, coastal real estate physical risk. Lower climate risk is a different risk profile, not a return promise.

Worked example

Hypothetical example: an ESG index holds 1 % in energy and 28 % in technology; its parent index holds 5 % in energy and 22 % in technology. All other sectors have equal weights in both.

Step 1 – active weights. Energy: 1 % − 5 % = −4 percentage points. Technology: 28 % − 22 % = +6 percentage points.

Step 2 – a year with energy +40 % and technology −10 % relative to the rest.
Relative return ≈ (−4 × 0.40) + (+6 × −0.10) = −1.6 − 0.6 = −2.2 percentage points. The ESG index lags the parent by about 2.2 points, with no "ESG effect" involved at all. In the mirror-image year it would lead by 2.2 points.

Step 3 – tracking error. Yearly relative returns over five years: +1.5, −2.2, +0.8, +2.2, −1.3 points. Mean = 1.0 / 5 = 0.2. Squared deviations: 1.69, 5.76, 0.36, 4.00, 2.25; sum 14.06; divided by (5 − 1) = 3.515; square root = 1.87 %. The 0.2-point average is far smaller than the 1.87 % noise, so five years cannot tell you whether the ESG index is "better".

Step 4 – the cost of fees. EUR 10,000 for 20 years at a hypothetical 5 % gross return: with a TER of 0.20 %, 10,000 × 1.048^20 = EUR 25,540; with 0.12 %, 10,000 × 1.0488^20 = EUR 25,933. The 0.08 percentage point gap costs EUR 393, about 1.5 % of the final amount: small but real.

Assumptions: hypothetical weights, returns and fees; no taxes, spreads or tracking difference beyond the TER.

Common mistake

Practice activity

On paper: an ESG index has 2 % energy and 16 % healthcare; its parent 6 % and 12 %, other sectors equal. (a) Relative return in a year with energy +25 % and healthcare −5 % relative to the rest? (b) Relative returns over four years were +0.6, −1.4, +1.8 and −1.0 points; sample tracking error? (c) Is the energy underweight mainly a transition-risk or physical-risk position?

Key takeaways

• Meta-studies show no systematic ESG penalty, but also no reliable premium; most results depend on period and definition.
• Short-term ESG index performance is mostly sector bets; active weight × relative sector return explains it.
• Tracking error tells you how far from the market you can land in any year; a few years of data prove nothing.
• Climate risk is split into transition and physical risk and is a measurable financial risk, not a return promise.

Next step

In the final lesson you will combine everything into a written sustainable investment policy with exclusions, label requirements and a look-through checklist.