MPs are set to receive a pay rise of 1.8 per cent this year, bringing their total salary to £77,379.

Announcing the decision, the Independent Parliamentary Standards Authority (IPSA) said it was increasing wages to keep them in line with public sector pay.

FactCheck looked at the bigger picture.

How much has MPs’ pay increased?

Salaries for MPs were first introduced in 1911 and were set at £400. That’s about £45,000 in today’s money.

Originally, they were designed to help poorer people who couldn’t afford to support themselves while working in Parliament unpaid.

We mapped how MPs’ wages have changed since then. The blue line shows the nominal value; the red line shows the wages in real terms, adjusted for inflation to 2017 values.

MPs’ real wages reached their peak in 2009 – the year the Expenses Scandal emerged. Since then, MPs have seen their wages fall slightly from £82,590 to £77,379 in real terms.

This recent dip was part of the justification given for the new salary system. A review in 2013 said: “MPs’ pay has fallen behind since the last review of their remuneration in 2007. There is a pay gap, a problem to be fixed.”

However, when we look longer-term, MPs have enjoyed handsome increases to their wages. Over the last thirty years, real terms pay has gone up by almost £20,000.

Do MPs’ wages really match the public sector?

MPs’ wages have always been considerably higher than the national average. But it has varied.

This graph, from a report by IPSA, shows MPs’ annual pay as multiple of UK average earnings, between 1911 and 2011.

Since 2015, increases to MPs’ pay have been formally fixed to changes in public sector earnings.

The results this produces might seem surprising. For instance, last year, public sector pay increases were frozen at one per cent, but MPs’ pay rose by slightly more than this.

This is because the calculation is based on public sector earnings – not salaries. So the effect of things like built-in pay increments, career progression and bonuses are reflected in MPs’ salaries.

The increases to MPs’ wages may be linked to the public sector, but what is this an increase from? And how was that base level set?

To answer that question, we need to look at a series of consultations and reports by IPSA in the years after the Expenses Scandal.

They looked at a number of different factors, including MPs’ pay as a multiple of national average earnings.

But they also looked at the wages of other senior officials, such as members of the judiciary, top civil servants, senior Army officers and public sector executives.

IPSA explained: “While they are helpful in setting a context to which many members of the public can relate, they should not be used mechanistically to set the level of pay.”

Ultimately, IPSA settled on £74,000 as the base level salary, claiming that MPs’ pay had been “artificially low for decades”.

Extra pay?

On top of MPs’ basic salary, there are opportunities for them to get more. For instance, all government ministers are entitled to an additional salary.

In 2017, this ranged from an extra £19,523 for a government whip, up to £77,896 for the prime minister (although she didn’t claim the full amount).

There are also extra payments available for the chairs of Select Committees. At the moment, this is set at £15,235, but it’s set to increase by £274 from April this year.

MPs can also claim expenses, covering things like transport and stationery. MPs living outside London are also able to claim for accommodation, with many renting flats in London on expenses.

In 2016/17, MPs claimed a total of £29.3m on expenses for themselves and their staff. That was up by £1.3m from the year before.