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An absolute exclusion removes every issuer that meets a stated disqualifying condition; a within-sector best-in-class screen keeps the stronger-ranked issuers in each peer group. Applied to the same universe, the rules can select different names and change sector weights in different ways. The benchmark matters because a screened portfolio may depart sharply from the exposure against which it will be judged.
Define the rule before selecting names
An exclusion can be tied to an activity, conduct or other mandate condition. A best-in-class process instead ranks comparable issuers within a sector and keeps those above a specified rank hurdle. CFA Institute describes both approaches in its ESG disclosure standards. A norms-based screen is another possible filter: it tests issuers against an external minimum standard, rather than a sector ranking.
The Sustainable Investing Certificate curriculum published by CFA Institute includes ESG portfolio construction and client reporting. For a candidate, the task is to connect the selection rule to the resulting holdings, then compare those holdings with the chosen benchmark. An ESG label alone does not tell you the rule or prove that the result fits a mandate.
Apply both screens to one illustrative universe
Assume an invented parent benchmark with equal weights in the four issuers below. The activity flag is a hypothetical mandate exclusion, and the ESG ranks are invented within each sector. These are teaching numbers, not observed securities or index data.
| Energy A | Energy | Yes | First | 25% |
| Energy B | Energy | Yes | Second | 25% |
| Technology A | Technology | No | First | 25% |
| Technology B | Technology | No | Second | 25% |
Under the absolute rule, exclude every flagged issuer. Technology A and Technology B remain; after equal reweighting, technology is the whole screened portfolio. Under a best-in-class rule that keeps the first-ranked issuer in each sector, Energy A and Technology A remain; after equal reweighting, each sector has half the portfolio. The parent benchmark also has half in each sector, so the second rule retains its sector split while the exclusion changes it completely.
The comparison is deliberately stark. A different starting weight or reweighting method would change the final weights. It would not change the key distinction: an issuer can win a sector ranking and still breach an absolute exclusion. If the mandate includes both rules, apply the exclusion as well as the ranking; do not assume that the latter overrides the former.
Read the benchmark rulebook
An ESG index can be used to compare returns, but its construction also determines which sectors and issuers are represented. Check the parent universe, each screen, the ranking peer groups, the reweighting method and the exposures left after screening. CFA Institute’s standards treat an ESG index as one whose construction incorporates ESG considerations; that definition does not specify a single screening method.
For a related study path, see the ESG programme page. The methodology page explains Omni’s approach to organising exam preparation.
After checking how screens change holdings and benchmark exposure, the strategic-allocation assumptions example shows the separate decision point where ESG research changes an asset-class return assumption before security selection.
Sources
- Sustainable Investing Certificate Curriculum | CFA Institute · cfainstitute.org · Retrieved
- Global ESG Disclosure Standards for Investment Products · cfainstitute.org · Retrieved
