The claim that "UK manufacturers need certainty and stability to be completely effective" is strongly supported by multiple independent lines of evidence: 1. **UK industry surveys** directly confirm the need. Make UK's Investment Monitor 2025 states that "frequent changes to tax policy remain one of the biggest barriers to business confidence and long-term planning," with 37% of manufacturers linking policy certainty to investment decisions. The MHA Manufacturing Report 2026 finds the "clearest message" from manufacturers is "the need for a stable, long-term policy framework that gives firms the confidence to invest, manage risk and deliver sustainable growth." Make UK's Executive Survey 2026 reports that detail needed to support planning and investment "is still missing." 2. **The UK government's own Industrial Strategy** (Invest 2035 green paper) is built on this premise, repeatedly stating the strategy aims "to deliver the certainty and stability businesses need to invest," acknowledging past strategies failed because they were "too short-lived." 3. **Academic research** establishes the causal mechanism. An NBER working paper using U.S. Census data on ~25,000 manufacturing plants found investment "strongly and robustly negatively associated with higher uncertainty," with uncertainty also negatively related to employment and sales growth. A separate NBER study using randomized information treatments found firms reduce prices, employment, investment, and sales as uncertainty increases. 4. **OECD cross-country analysis** estimates a one standard deviation increase in economic policy uncertainty reduces business investment growth by ~1 percentage point after one year, accounting for approximately one-sixth of the investment shortfall since the global financial crisis. The causal link is confirmed by experimental and quasi-experimental research, not merely correlational. A minor caveat is that "completely effective" is a strong phrase and other factors (skills, energy costs, supply chains) also matter, but the evidence consistently shows certainty and stability are necessary conditions for manufacturers to operate at full effectiveness. **Sources:** - Make UK, Investment Monitor 2025 — https://www.makeuk.org/insights/reports/investment-monitor-2025 - Make UK, Executive Survey 2026 — https://www.makeuk.org/docs/executive-survey-2026pdf/download?attachment= - MHA, Manufacturing Report 2026 — https://www.mha.co.uk/spotlight-on/mha-manufacturing-report-2026 - GOV.UK, Invest 2035: The UK's Modern Industrial Strategy (green paper) — https://www.gov.uk/government/consultations/invest-2035-the-uks-modern-industrial-strategy/invest-2035-the-uks-modern-industrial-strategy - GOV.UK, Industrial Strategy Policy Paper (PDF) — https://assets.publishing.service.gov.uk/media/69256e16367485ea116a56de/industrial_strategy_policy_paper.pdf - NBER, "Investment and Subjective Uncertainty" (Working Paper 30654) — https://www.nber.org/system/files/working_papers/w30654/w30654.pdf - NBER, "The Effect of Macroeconomic Uncertainty on Firm Decisions" (Working Paper 30288) — https://www.nber.org/system/files/working_papers/w30288/w30288.pdf - OECD, Economic Outlook Volume 2025 Issue 1 — https://www.oecd.org/en/publications/2025/06/oecd-economic-outlook-volume-2025-issue-1_1fd979a8/full-report/reigniting-investment-for-more-resilient-growth_99b36090.html