Cornwall may not have been poor enough to justify receiving £1bn of European Union funding, it has emerged.
In recent years the county has several times been listed at the bottom of the poverty table in England and Wales.
But revised GDP figures suggest Tees Valley and Durham, South Yorkshire, and West Wales and the Valleys are now all more deserving of EU money.
Experts say that could make it harder for Cornwall to get funding post-Brexit.
Major beneficiaries include the Eden Project, Combined Universities in Cornwall, Newquay Airport and a project to bring superfast broadband to the county.
There's no suggestion the money must be paid back.
Pete Ledingham, director of grant-aided firm Geothermal Engineering said the recalculation was "staggering".
"I would have thought the need was obvious in Cornwall and has been for a long time," he added.
Areas with a GDP of less than 75% of the average EU GDP qualified for funding as they were below the EU's poverty threshold.
But revised figures Cornwall was never actually below the threshold used to award grants such as Objective One, which provided some £400m to the county.
Neil Gallacher, BBC Spotlight's Business Correspondent
It's hard to get your head around. As recently as a couple of years back, the official statistics showed that when Cornwall started getting Objective One in 2000, its economy stood at 68% of the EU average.
Now that statisticians have a supposedly better way of measuring, the same league table shows that in 2000 Cornwall's economy was actually on 83%.
The basket of things they add up has altered. Oddly, although this new picture shows Cornwall in a better light, it leaves West Wales firmly at the bottom of the league table.
Cornwall IS poor; just not THAT poor.
Cornwall councillor Candy Atherton said trying to get money for the country from central government "is like trying to get blood out of a stone".
She added: "Goodness knows where our economy would have been if we hadn't had that injection of funds."
Local businessman Russell Dodge said he was "horrified" and in "deep shock" about the recalculation.
The MD of Business Location Services Ltd said: "EU funding has had a massive impact on the Cornish economy and without it we certainly wouldn't be where we are today.
He warned that the recalculation may affect central government funding to the county once the UK leaves the EU.
"The government is going to look on Cornwall in a different light, notwithstanding the GDP issue there are still major structural weaknesses in the Cornish economy," he said.
Economist Peter Gripaios said the new figures are a "pretty significant revision" but are "probably more accurate".
"If they'd been that accurate back in 2000 then it's quite possible Cornwall wouldn't have got Objective One and would have missed out on quite a lot of European funding."
Labour Mayor of Middlesbrough, David Budd, said he would now be getting back in touch with the local government secretary to ask what would be done to replace EU funding for the Tees Valley.
"Places like Tees Valley and Cornwall have had great benefits from European funding for many years and it's vital the government finds a way of replacing this funding," he added.