Firms about to become exporters were 26% more productive than firms that never exported in World Bank analysis.
Source
World Bank — https://blogs.worldbank.org/en/endpovertyinsouthasia/global-integration-can-spur-productivity-growth-pakistan. Verified in source set / retroactive normalization pending.
What it proves
More productive firms self-select into export markets.
How to deploy: Use Firms about to become exporters were 26% more productive than firms that never exported in World Bank analysis. (Firms about to become exporters were 26% more productive than firms that never exported in World Bank analysis., None) to support the claim that More productive firms self-select into export markets.
What it does not prove: The 26% gap is measured before these firms exported, so it identifies self-selection, not any benefit of exporting — it tells you who clears the threshold, not what crossing it does. The comparison also runs only over firms that eventually succeeded in exporting, so productive firms that tried and failed are absent, and the universe is formal firms with usable accounts, a sliver of an economy that is over 85% informal.
Memory hook: 26% → exporters were already better before they ever shipped abroad
Rebuts the claim: 'Give ordinary firms an export subsidy and they will become exporters' — the productivity gap exists before entry, so a rebate cheque cannot manufacture an exporter out of a firm that was never near the threshold.