One of the most persistent claims in public debate is that high levels of immigration are necessary to support an ageing population.
It sounds intuitive. As birth rates fall across the West, the argument follows that we must import working-age people to sustain the system.
But when you look more closely at the data, the picture becomes less certain.
At its core, this is a simple question:
How many people are working – and how many depend on them?
The Active Dependency Ratio (ADR) captures this directly. It measures how many inactive adults – those not working or seeking work – rely on every 1,000 active workers.
A rising ADR means increasing pressure on those who are working to support those who are not.
The projections used here draw on the Office for National Statistics (ONS) 2022-based population projections, with participation rates held constant using Office for Budget Responsibility assumptions.
It is not a perfect measure. But it is an honest one.
The ONS models four long-term migration scenarios:
Zero net migration
Low migration (120,000 per year)
Principal projection (340,000 per year)
High migration (525,000 per year)
When we apply these scenarios to the ADR, a clear pattern emerges.
Across all scenarios, the direction of travel is the same: the dependency burden rises.
Higher migration slows the rate of increase – but it does not change the outcome.
Even under the highest migration scenario, the result does not differ in kind. It simply arrives later.
Put plainly: compared with the principal projection, very high migration delays the UK reaching an ADR of 700 by roughly nine years.
That is not a resolution.
It is a postponement.
The ONS also models four different fertility scenarios, from low through to replacement Total Fertility Rate (TFR):
Low variant – 1.25 long-term TFR
Principal variant – 1.45 long-term TFR
High variant – 1.65 long-term TFR
Replacement Rate Fertility – 2.1 long-term TFR
Because the ADR only includes those aged 16 and over, the effects take time to appear. But the long-term differences are meaningful.
Even modest increases in fertility begin to shift the trajectory.
A return to replacement-level fertility extends the timeline to reach an ADR of 700 by several decades.
This is not a complete solution. Longer life expectancy still increases the older population.
But it highlights something important:
Not all demographic levers operate in the same way.
Some reshape the system. Others merely defer its pressures.
There is a third factor that receives far less attention – and may be more powerful than either migration or fertility.
Participation.
Dependency is not simply about age. It is about whether adults are active in the labour market.
What happens if more people of working age are actually working?
Consider a scenario where participation rates increase by 10% across age groups.
The effect is striking.
Under this scenario, the UK does not reach an ADR of 700 until well into the next century.
This is, of course, a model – but it illustrates where the real leverage may lie.
Not in expanding the population indefinitely, but in enabling more people within it to contribute.
The pattern across all scenarios is consistent.
Immigration can ease the pressure for a time, but it does not resolve the underlying dynamic. Over time, it creates its own dependency cycle, requiring ever-increasing inflows to maintain balance.
A more durable answer lies closer to home:
enabling people who want families to have them
increasing participation across all ages
improving health so more people remain active for longer
raising productivity per worker
This is where the real leverage sits.
Demographics shape the future.
This is a conversation worth having – calmly, honestly, and with the data in view.
The Truth Contract – not just more content, but a commitment.
You’re here because the surface story doesn’t hold.
You’re ready to question, contribute, and help shape a future worth showing up for.
This is the contract: Truth. Action. Together.
Add your voice to the conversation. This is how we grow the mandate for change.
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