The Demographic Squeeze

Not a question of whether migration is "good" or "bad" — a mechanical look at what's actually happening to the UK's births, deaths, and population, using the ONS's own numbers.

The two forces at work

A country's population grows or shrinks from two independent sources: natural change (births minus deaths) and net migration (people arriving minus people leaving). The UK's total fertility rate is now around 1.49 children per woman — the lowest on record, and well below the 2.1 "replacement rate" needed to keep a population stable without migration. As a result, the gap between births and deaths has been shrinking for years, and the ONS's own April 2026 projections confirm that deaths are expected to exceed births every year from mid-2026 onward.

Oxford's Migration Observatory, analysing the same ONS projections, found that net migration accounts for 144% of the UK's projected population growth between 2025 and 2039 — mathematically, more than the entirety of the growth, because natural change is itself negative over that period. Under a hypothetical zero-net-migration scenario, ONS projections show the UK population would begin declining from mid-2025 onward.

This is why migration and population size can't really be treated as two separate policy questions — under current demographic trends, a decision about migration levels is, mechanically, also a decision about whether the UK's population grows, stays flat, or shrinks.