The datasets used by index-based ESG approaches most likely:

Index-based ESG strategies rely on datasets thatoften lack long-term historical data, which limits the ability to test ESG factors across multiple market cycles. Thisshort dataset historyintroduces risk and uncertainty into ESG portfolio construction and can impact back-testing reliability.

“The length of history of datasets” is a key consideration when evaluating ESG data providers, with current ESG ratings and data often “not tested across full economic cycles.”

Option A overstates the level of global comparability, and Option C is incorrect because much ESG data comes fromvoluntary disclosuresor third-party estimates, not just mandatory filings.