Welcome to Reality Check. Today I'm examining the political argument over National Insurance.
Gordon Brown and David Cameron have again traded blows on the issue in their final Commons clash before the election.
The Conservative leader argued Labour would "kill" the economic recovery with the planned 1% National Insurance increase, due to take effect next year.
The Tories, who have the backing of more than 60 business leaders on the issue, have pledged to reverse most of the proposed rise if they take power.
Cameron and Brown clash over National Insurance and spending plans at PMQs
But the prime minister said that would mean spending cuts that would threaten vital public services as well as Britain's economic recovery.
So who has got it right?
In order to answer that, you would have to take a view on whether the economy can withstand the £6bn of public spending cuts which the Tories would make in the current year, to make up for the revenue that they would lose by not implementing that tax rise in full.
Some would say they are arguing over a relatively small amount. The 1% rise in NI is expected to raise about £7bn a year. Government receipts for 2010-11 are expected to total £541bn, while the deficit is forecast at £167bn.
But Labour says such cuts would jeopardise the recovery. Economists are split on whether Labour is right.
Actually, even before making that judgment, you have to decide whether it's possible to eliminate £6bn of so-called government waste as quickly as that.
Then you would need to make a judgment about whether companies really would shed jobs or choose not to hire new people if the cost of employing them were to go up due to the National Insurance increase.
Common sense suggests that if the cost of employing people rises, all other things being equal, companies will indeed hire fewer people.
And the Tories say that if every major business lobby group plus 69 individual business leaders are making that point, well it must be credible - since these are, to state the obvious, important employers.
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