The Decisive
Decade

The standard tool for decomposing a national productivity number is the shift-share. Aggregate productivity growth is split into three components: the within-industry effect (each sector's own productivity gain weighted by its base hours), the between-industry reallocation effect (hours moving towards more or less productive sectors), and a cross term capturing the interaction:

ΔP = Σ s_i,0 · ΔP_i  +  Σ P_i,0 · Δs_i  +  Σ ΔP_i · Δs_i

The middle term — Σ Pi,0 · Δsi — is where the British problem lives. For several consecutive quarters, it has run negative. Hours are not just failing to grow inside high-productivity sectors. They are leaving them.

The principal beneficiary of those hours is the health and social care sector, where output per hour has fallen by roughly 19% since 2019 — the steepest fall in any major industry. Financial and insurance activities, historically the single largest contributor to UK productivity growth, has shown stagnant output with rising hours, contributing −1.2% against its 2019 baseline. Information and communications, where the global frontier has accelerated sharply, has seen its UK productivity growth roughly halved since the pandemic; its contribution to national growth has fallen from 84% (combined with Finance and Manufacturing) to under 34%.

Between 2013 and 2022, GVA per head in the North of England averaged £22,710, against £29,379 in the rest of England — a gap of roughly 30%. Standard regional models attribute the gap to capital, skills and industrial composition. The more recent decomposition work, published by the Northern Health Science Alliance and replicated by the IFS, attributes 36% of it directly to differences in regional health.

Since the pandemic, that wedge has widened. The gap in economic inactivity due to long-term sickness between the North and the rest of England has nearly quadrupled, from 1.1 percentage points to 4.2 percentage points. Long-term ill-health inactivity in the North East stands at 9.5%, more than double the South East's 4.5%. Closing the gap is estimated to be worth £18.4 billion annually in additional GVA — a figure larger than the entire annual capital settlement of the Department of Health and Social Care.

This is the line at which the productivity story and the fiscal story become the same story. A working-age population that cannot work because it is unwell appears on the national accounts as a labour participation drop, on the public-finance forecasts as a higher welfare bill, and on the NHS balance sheet as a longer queue — three different ledgers, one underlying mechanism.

The most distorting single feature of the British income tax system is hidden between £100,000 and £125,140 of adjusted net income. Inside that band, the standard 40% higher rate interacts with the tapered withdrawal of the £12,570 personal allowance at the rate of £1 for every £2 of earnings above £100,000.

Let ANI denote adjusted net income in the trap band and A0 the maximum personal allowance of £12,570. The remaining allowance is:

A(ANI) = A₀ − ½ · (ANI − 100,000)

Each additional £1 of gross income therefore raises taxable income by £1.50: the £1 itself, plus £0.50 of allowance lost. Apply the 40% higher rate to the adjusted £1.50:

MTR = 0.40 × 1.50 = 0.60 ⇒ 60%

Add the employee National Insurance contribution that still applies inside the band, and the effective marginal rate on earned income reaches roughly 62%. Above £125,140, the personal allowance is fully withdrawn, the taper effect ends, and the marginal rate drops to the additional rate of 45%. For a substantial range of professional earnings, the marginal tax rate on the next pound is materially higher than the rate paid by anyone earning more than £125,140.

First past the post was designed for a two-party electorate. Applied to a five-party electorate, it becomes a non-linear amplifier that rewards geographically concentrated support and punishes evenly distributed national support. The formal condition is unremarkable: in a constituency c with candidates i, the winner w satisfies vw,c > vj,c for all j ≠ w. There is no majority requirement.

The consequence is the cloning paradox. If a right-of-centre majority is split between two candidates — Conservative on 23%, Reform UK on 23% — a progressive candidate can win the seat on 25%, despite 46% of the constituency preferring a socially conservative representative. The math is symmetric: a progressive bloc split between Labour, Liberal Democrats and Greens delivers the seat to a unified right-wing challenger on a low plurality.

The 2026 ward-level data tells the same story at scale. Reform UK averaged 40% of the vote in council wards where 2016 Leave support exceeded 60%, and just 10% in wards where Leave support was under 40%. Reform sweeps post-industrial, coastal and working-class wards while wasting votes across urban, highly educated municipal zones. The Greens do the symmetric thing in reverse. Both parties become structurally over-represented in the seats they target and structurally under-represented in the seats they cannot win.

The centre-squeeze follows. Under any system that rewards intense first-preference support over broad acceptability, the Condorcet winner — the candidate a majority of voters would tolerate as a second or third choice — is the candidate most likely to be eliminated first. Under FPTP, the major parties respond by pulling towards their own wings to defend their bases from the bloc challengers, hollowing out the centre that, on paper, still represents most voters.

Read in isolation, none of the four mechanisms surveyed here would close on itself. A productivity squeeze can be reversed by capital investment. An asset divide can be loosened by housing supply. A tax trap can be flattened by primary legislation. An electoral fragmentation can be absorbed by a reformed voting system or a redrawn party landscape. The reason the next ten years are unusually constrained is that the four mechanisms feed one another.

Frozen thresholds and the 62% marginal rate accelerate high-skill emigration. Emigration shrinks the productive tax base. A shrinking tax base raises the political cost of any tax cut at the top and pushes the burden further onto middle earners through further fiscal drag. Reduced disposable income reduces private demand. Public expenditure on health and care — the sectors where output per hour is falling fastest — carries an increasing share of measured GDP. Higher state spending against a shrinking productive base produces the conditions for further marginal-rate increases. The loop closes on itself.

The electoral channel is the multiplier. A five-way fragmented electorate, governed under FPTP, produces parliaments in which 25–30% pluralities deliver working majorities. Each such government has both the incentive and the formal power to make large structural changes against the preferences of two-thirds of voters. The result is policy that swings sharply between parliaments, deters long-horizon private capital, and reinforces the conditions for further fragmentation at the next election.

Five structural interventions, each addressing one of the load-bearing mechanisms above, would be sufficient to move the 2036 envelope from the second column to the first. None is partisan.

1. Abolish the earned-income tax traps. Flatten the personal allowance taper between £100,000 and £125,140. Eliminating the 62% marginal rate restores a smooth tax schedule, removes the largest single behavioural distortion in the system, and reduces the financial premium on high-skill emigration.

2. Lift Gross Fixed Capital Formation off the bottom of the G7. Move GFCF from 18.9% of GDP toward 22%. This requires the planning and regulatory reforms covered in The Wiring Diagram — rules-based zoning, MCA fiscal autonomy, professionalised civil service procurement — applied with the explicit objective of unlocking private capital for housing, energy, digital and transport infrastructure.

3. Resolve the health-productivity nexus. Direct preventive health and primary care investment at the regions where long-term sickness inactivity has quadrupled since 2019. The £18.4bn annual GVA prize from closing the North-South health gap exceeds the marginal cost of the intervention.

4. Align immigration with productivity. Reform the Earned Settlement scheme to lower the financial and temporal barriers for critical public-service workers — particularly in health and social care, where the productivity drag binds tightest. Retain the fast-track for high earners; close the cliff-edge for the workers who keep the largest single productivity-drag sector running.

5. Plan for the permanent five-party electorate. Whether or not the voting system changes, the electorate has. Mainstream parties that continue to design strategy for a two-party world will continue to deliver governments elected on minority pluralities under conditions of permanent within-bloc volatility. The constitutional question is whether to absorb the volatility through proportional reform, or to manage it indefinitely.