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In 1942 the US ran a federal budget deficit of 14.8 per cent of GDP; in 1943 30.8 per cent; in 1944 23.3 per cent; and in 1945 22.0 per cent – a four-year average deficit of 22.7 per cent of GDP.

Today, in 2010, the US is running a federal budget deficit that the CBO estimates at 10.3 per cent of GDP. Its score of Obama’s budget proposals has that deficit falling next year to 8.9 per cent of GDP, then over the next two years to 4.5 per cent of GDP, and remaining in the 4-5 per cent of GDP range for the rest of this decade – for an average CBO-scored Obama policy deficit of 5.3 per cent over the next eight years.

Compare that to the Great Depression: in Roosevelt’s disastrous 1937-38 fiscal austerity and monetary tightness experiment, the US federal government deficit shrank to 2.8 per cent and then to 0.5 per cent of GDP; otherwise the deficit bounced around between 3.8 per cent and 5.5 per cent of GDP between Roosevelt’s inauguration and the end of the 1930s – for an average deficit in the years outside the disastrous austerity experiment of 4.6 per cent of GDP between Roosevelt’s inauguration and the second world war.

So 22.7 per cent, 4.6 per cent, 5.3 per cent: the New Deal’s 4.6 per cent looks a hell of a lot more like our forecast 5.3 per cent than the second world war’s 22.7 per cent does. On first reading, I simply did not understand how Ferguson could with a straight face claim that “what we are witnessing today has less to do with the 1930s than the 1940s: it is world war finance without the war.”

On looking again, I found in Ferguson’s piece the sentence: ”The federal debt burden rose only slightly – from 40 to 45 per cent of GDP – prior to the outbreak of the second world war...”

On June 30, 1933 the US federal debt was $22.5bn – 40 per cent of 1933 GDP. By June 30, 1941 the US federal debt had more than doubled to $49bn – 87 per cent of 1933 GDP. That’s a big increase. How can that mesh with Ferguson’s observation that “the federal debt burden rose only slightly... prior to the outbreak of the second world war”? Look at nominal GDP: it grew from $56.4bn in 1933 to $126.7bn in 1941. Even a more-than-doubling of debt will not raise the debt buden if economy-wide spending more than doubles as well.

But that does not mean that deficits in the 1930s were an order of magnitude smaller than the deficits we are looking forward to today, or that today’s fiscal picture looks more like that of the second world war than like the picture of the New Deal.