Why economic projections are not facts

[RandBlade]

https://www.ft.com/content/dde5cd74-...4-2218e7146b04
Thought I'd take this out of the Brexit megathread but some fascinating data came out today on the UK's national budget deficit. The OBR (Office for Budget Responsibility) makes predictions twice a year as to what the state of the economy is and will be, in March and November.

Long story short: the OBR's March 2018 borrowing forecast was £5bn too high for the year ending in March 2018.

Or if we look back further its November 2017 borrowing forecast was £10bn too high and the forecast from March 2017 was £18bn too high.

Likewise its March 2017 borrowing forecast for the year ending March 2017 was again £5bn too high and its November 2016 borrowing forecast for that year was £22bn too high.

[GGT]

Aren't forecasts and projections always adjusted in hindsight?

[RandBlade]

All the time but irritatingly some people take a forecast as the gospel truth instead of the wild semi-educated stab in the dark that it is.

[GGT]

Well, why were the borrowing projections off between 5 and 22 Billion? Sounds like a pretty big margin of error

[RandBlade]

That was my point. Especially to be off by £5 billion in March when measuring until March.

Not even forecasting years into the future.