UNA DEFENSA DE REINHART Y ROGOFF por John Phelan:

In truth the idea that there was an Iron Law such that an economy would shrink as soon as it’s government debt hit 90 percent of GDP, the ‘strong form’ of Reinhart and Rogoff (pushed more by the political practitioners than them it ought to be said), was always iffy. It smacks of the sort of bogus causation derived from correlation which is the basis for much modern macroeconomics.

There are, for example, different types of debt. Advocates of higher spending often point to the 260 percent of GDP the British government owed in 1816, the 180 percent it owed in 1919, or the 220 percent it owed in 1945. This, they tell you, proves that Britain’s economy can bear an even greater burden of debt than the 70 percent of GDP it has doubled to in the last five years.

But you don’t have to be David Starkey to know that in 1816, 1919, and 1945 Britain had run up that debt to pay the cost of defeating a tyrant and as soon as that was done we stopped. It was an expense we had to meet and defray over time, the wartime borrowing was classic ‘consumption smoothing’.

To put it another way, when the British government started spending heavily in 1792, 1914, or 1939 there was a definite endgame for this spending: the restoration of the Bourbon monarchy, the defeat of the Kaiser, the overthrow of Hitler. The very moment those goals were accomplished spending would fall rapidly.

Our current level of government spending, by contrast, is not being undertaken to safeguard this country and its neighbours from conquest but to maintain a public sector and welfare state grown fat on borrowing and tax revenue from an unsustainable bubble in the absence of that bubble and those tax revenues. We are not smoothing consumption, we are sucking it out of tomorrow. And, unlike Pitt the Younger, Herbert Asquith, or Neville Chamberlain, present day advocates of higher spending cannot give an endgame for their proposed accrual of debt.
The point of this for evaluating Reinhart and Rogoff’s work is to note that one load of debt is not necessarily the same as another. There ought to be a little nuance to the picture, there are no magic numbers.

[...] despite what some excitable commentators have proclaimed, Herndon, Ash, and Pollin have not found no correlation between high debt and low growth. They have found a weaker one than Reinhart and Rogoff in 2010 and about the same as they found in 2012, but they have still found one.
As page 21 of their paper states: if debt is below 30 percent GDP growth comes in at 4.2 percent, if debt is between 30 percent and 60 percent of GDP growth comes in at 3.1 percent, if debt is between 60 percent and 90 percent of GDP growth comes in at 3.2 percent, and if debt is over 90 percent of GDP growth comes in at 2.2 percent. Even on Herndon, Ash, and Pollin’s figures higher debt is correlated with lower GDP growth.