Tax incidence — who really pays

Tax incidence is the question of who really pays a tax — not who the law tells to remit it, but who bears the economic burden after market prices adjust. The empirical answer is usually surprising and politically inconvenient. The theory is clean enough to be taught in 45 minutes; the applications take a career to master.

Statutory vs economic incidence

Statutory incidence is which side of a transaction the law obliges to send the money to the tax authority. Economic incidence is which side ends up worse off after prices and quantities adjust. These two are almost never the same.

Example: Kenya's 16% VAT on commercial-vehicle imports.

• Statutory incidence: the importer remits VAT to KRA.
• Economic incidence: depends on the elasticities. If the supply of vehicles is highly
  elastic (importers can shift to other markets) and demand is relatively inelastic
  (Kenyan freight operators need vehicles, no good substitutes), most of the
  burden falls on the buyer through higher prices. If demand is elastic and supply
  inelastic, the importer absorbs most of the tax through lower margins.

The statutory remitter is irrelevant to the economic question.

The elasticity-share formula

Three diagnostic cases:

• Perfectly inelastic demand (εd = 0). Buyers can't reduce their consumption (e.g., insulin for diabetics). Buyers bear 100% of the tax regardless of statutory incidence.
• Perfectly elastic supply (εs = ∞). Producers can shift to alternative uses or markets at unchanged net return (e.g., world-market commodity producers in a small country). Buyers bear 100% of the tax.
• Symmetric elasticities (εs = εd). Burden splits 50/50.

Why incidence is almost always on the inelastic side

The general empirical regularity: necessities (inelastic demand) and immobile factors (inelastic supply) bear most of the tax burden in their markets. Examples:

• Tobacco excise — demand is inelastic (addiction). Smokers bear the burden. Used deliberately for both revenue and behaviour modification — a 'sin tax'
• Land — supply is perfectly inelastic (you can't make more of it). Land taxes are entirely borne by landowners. This is why land-value taxation is the most efficient tax in pure theory (Henry George 1879) and why it remains under-used in practice (landowners vote)
• Labour — labour supply is moderately inelastic for prime-age workers. Payroll taxes (PAYE, NSSF, NHIF) are largely borne by workers as lower take-home pay, regardless of whether the law says employer or employee remits
• Fuel — diesel demand is inelastic in the short run for freight operators with no immediate alternatives. The Kenya fuel levy (KES 18/litre on petrol, KES 18/litre on diesel as of 2025) is mostly passed through to consumers in pump prices and onward to freight rates

The corporate income tax — the most misunderstood incidence question

Statutory incidence of corporate income tax is on the corporation. Economic incidence is split between (a) shareholders through lower after-tax returns, (b) workers through lower wages, and (c) consumers through higher prices. The exact split is contested and depends on capital mobility, labour mobility, market structure, and the time horizon.

• Closed-economy long-run consensus: ~60% on capital, ~40% on labour (Harberger 1962; refined by Auerbach 2006)
• Open-economy small country: most of the burden shifts to labour because capital can leave (Mutti & Grubert 1985; Hassett & Mathur 2006). In an integrated capital market like East Africa, this is the empirically relevant case — a Kenyan corporate-rate increase falls more on Kenyan workers than on shareholders, because shareholders can shift capital to Uganda, Rwanda, or further afield
• Time matters: in the short run, capital can't move and bears more of the burden; in the long run, capital adjusts and labour bears more

African-context incidence questions

VAT on basic food (the regressive vs progressive debate)

VAT incidence on food: highly inelastic demand for staples (maize meal, ugali ingredients, basic vegetables) → buyer-side incidence is near 100%. So a VAT increase on staple food is fully passed through to consumers. Because food is a larger share of low-income household budgets (Engel's law), the absolute incidence is regressive in budget-share terms even if everyone faces the same VAT rate. This is the empirical basis for the redistribution argument against staple-food taxation — though as the optimal-taxation module showed, the right answer is to tax broadly and redistribute via direct transfers, not to exempt the staple.

Fuel levy — who really pays?

Kenya's fuel levy is statutorily on the importers/distributors. Economic incidence: diesel demand from commercial freight is short-run inelastic → most of the levy passes through to freight rates. Freight rates pass through to most goods (Kenya's economy is heavily road-freight dependent) → the levy is effectively a general consumption tax with a fuel-distribution pattern. Inflation impact estimates from the Kenya National Treasury put the pass-through at ~85% to retail prices within 3 months of a levy change.

Excise on mobile-money transfers

Kenya raised the excise duty on mobile-money transactions from 12% to 15% in 2021. Statutory incidence: telco. Economic incidence: M-Pesa demand is moderately inelastic for many users (network effects, no good substitute) and supply is elastic in the relevant range (telcos can adjust fee schedules). Result: passed through almost entirely to customers via higher per-transaction fees. Volume-elasticity studies (CGAP 2022) found a -0.15 to -0.3 demand elasticity, implying buyers absorbed most of the rate increase with a modest volume drop.