How many people are disabled?

It depends how you define it. Government surveys suggest that 20 per cent of people in the UK consider themselves disabled.

The older you are, the more likely you are to report a disability. Some 7 per cent of children, 17 per cent of working-age people and 45 per cent of pensioners say they are disabled.

In 2010, the OECD said 35 per cent of Britons said they had a “long-standing illness or health problem”, compared to an average of 30 per cent across the EU.

How many are in work?

The government says it wants to halve the disability employment gap – that is, the difference between employment rates among the disabled and non-disabled population.

The employment rate among working-age disabled people was 46.7 per cent at the end of 2015, compared with 80.3 for the non-disabled. Halving the gap will mean bringing  1.2 million more disabled people into work.

How much state support do disabled people receive?

Experts caution against making comparisons between the benefits systems of different countries, as it is hard to be sure that you are comparing like with like.

For what it’s worth, the OECD tries to count all spending on “sickness, disability and occupational injury” in wealthy countries and says Britain spent 2.5 per cent of national wealth in 2011, more than the average of 2.2 per cent.

The big problem here is which benefits you include in the total.

Politicians from all sides tend to change the definition of disability benefits spending when it suits them, either narrowing the focus to talk about Personal Independence Payment (PIP) and its predecessor Disability Living Allowance (DLA), or taking in every conceivable disability, incapacity, or sickness payment.

Which benefits have been cut?

The last government changed the eligibility rules for the main disability benefit PIP, which is gradually replacing DLA. There were fears that this would lead to fewer people being paid at the higher rate.

It also decided to pay a new lower rate for less disabled claimants, and raise the amount given to the most severely disabled.

In 2012 the coalition cut the length of time some claimants could receive the main incapacity benefit – Employment and Support Allowance (ESA).

From April next year new ESA claimants will no longer be entitled to an extra £29.05 for taking part in “work-related activity”. There will be a corresponding cut to a similar part of the Universal Credit system.

Other welfare reforms like changes to uprating, freezing and capping benefits for the non-disabled could affect families with disabled people too.

So who is worse off?

We know that some individual claimants are worse off financially and others are better off as the result of the last government’s policies.

It’s probably impossible to construct an “average disabled person” and say whether they have won or lost, since individual circumstances will affect what you can and can’t claim.

Certainly researchers from think-tanks like the Institute of Fiscal Studies have not attempted to do this.

The government likes to claim that is increasing the total amount spent on the main benefits, not cutting it.

Is this true? It depends on which payments you are talking about.

The amount spent on PIP and DLA is forecast to rise in real-terms over this parliament, after a cut planned by the then-chancellor George Osborne at the last budget was reversed.

ESA spending is set to fall slightly in real terms.

In both cases the numbers of people claiming the benefits is also predicted to go up, so a rise in spending doesn’t necessarily mean the payment per person will become more generous – it could mean the opposite.

If you include all disability and incapacity benefits, as well as other things like payments for people injured in industrial accidents, housing benefit for the sick and disabled, carers’ allowance and so on, it’s possible to find evidence of a small real-terms cut over this parliament.

Have the changes saved money?

Since spending on the main disabled benefits are going up in real terms, it follows that the last government failed to make significant savings.

According to this 2012 impact assessment, the change from DLA to PIP was supposed to save the equivalent of “20 per cent of forecast working-age DLA expenditure… returning-working age DLA spending to 2009/10 levels in real terms.”

The actual amount spent was around £3.6bn more than this figure.

It was a similar story with ESA. There were supposed to be hundreds of thousands fewer claimants and a similar saving of around £3.5bn. N materialised.

Jonathan Portes from the think-tank NIESR wrote about this in detail last year, saying: “I have described this whole episode – costly and painful for claimants and taxpayers alike –  as the biggest single social policy failure of the last 15 years.”

There’s a pattern here: the government changes the eligibility criteria and testing regime for the benefits, only to find that the numbers of claimants, and the cost to the taxpayer, continues to go up.

OBR figures show how the coalition consistently overestimated the amount of money that would be saved from changes to disability benefits:

Why are more people claiming disability benefits?

There doesn’t appear to be one simple answer to this. The UK population is growing, and ageing, and older people are more likely to be disabled.

Perhaps the launch of a new “brand” of benefit like PIP makes people more likely to claim.

Last year the Institute for Fiscal Studies noted “systematic growth in the proportion of claimants with mental and behavioural disorders as their principal health condition, rather than physical health problems”.

Deputy director Carl Emmerson said at the time: “It’s implausible that people have become more mentally unhealthy on this scale and this time horizon.

“The problems we have seen have always been there and the system is picking them up. Whether it’s a triumph because people’s mental health problems are being recognised or the system is not working, we don’t know.”

What’s happening under Theresa May?

The work and pensions secretary, Damian Green, has said there will be no more benefits cuts under Theresa May’s government.

But legislation that has been passed but not yet come into force will go ahead in this parliament.