GDP is a measure of the total economic activity in the UK. It’s calculated using surveys commissioned by the Office for National Statistics. GDP is so complex that it comes out in separate parts, meaning that early estimates can be revised as new data comes out. As such, they’re published in four different forms, each with more detail and coverage than the last:
Preliminary estimates happen first, which just contain main GDP estimates and a breakdown of these across different industries of the economy.
Second estimates come out a month later, and add in growth figures on trade, investment, household spending, measures of inflation (GDP deflators) and international comparisons of GDP.
Quarterly national accounts are published a month later still, and add in figures for households’ disposable income and savings, and which sectors of the economy are borrowing or lending.
The Blue Book is published annually and contains everything about the UK’s national accounts from the previous year.
For the wider context, GDP figures can be traced back to the Second World War using the ONS’s key economic time series data.
Figures actually exist as far back as the 1800s, but these obviously rely on several different sources which don’t fit perfectly together. The Bank of England compiles this data, along with data tables, but we should use the numbers with caution.
The Office for Budget Responsibility forecasts what is expected to happen to GDP over the coming years. These figures have large margins of error for obvious reasons, and are only broadly indicative. The OBR publishes the numbers as public finance forecasts.
Meanwhile, banks and academics all produce their own estimates. Helpfully, HM Treasury collects all these forecasts in one monthly release.
Productivity figures measure the output of workers either per worker, per job or per hour worked, as well as what workers cost. They can show which industries and regions add more value to the economy than others.