NEW YORK ( BBH) -- In its Fiscal Monitor published in November, the International Monetary Fund made a crucial point about growth rates and debt dynamics. It pointed out that the larger the differential for any country between real interest rates (borrowing costs) and real growth (with the differential defined as r-g), the larger the increase in the primary budget balance (budget ex-interest payments) that is needed just to stabilize the debt/gross domestic product ratio. The IMF did a comprehensive study across both developed markets and emerging markets, noting that EM countries typically have negative r - g due in large part to high growth rates, while DM tend to have positive r - g due in large part to low growth rates. We have long posited that eurozone efforts so far to address the crisis are likely doomed to failure because of this basic concept from the IMF. Borrowing costs (r) have risen, not fallen, despite the Greek and Irish bailouts, despite the European bank stress tests, despite the creation of the European Financial Stability Facility. On the other hand, fiscal austerity measures are keeping growth (g) very low for most of the eurozone, and so those countries are forced into even greater austerity (running bigger primary surpluses) in order to prevent debt ratios from blowing out even more. To us, this is akin to bailing water from a sinking ship at the same rate that the water is coming in. The ship can stay afloat, but the actual hole is not being addressed and so it will eventually sink when the person bailing finally tires. Markets have fixated on 7% borrowing as some sort of threshold for a country having to go to the EFSF. We would posit that under the IMF concept of r - g, borrowing costs don't even have to rise that high to help unravel a country's debt dynamics. Let's look at IMF growth forecasts for 2011 for the major eurozone countries and compare them to real 10-year borrowing costs to obtain r - g. The differential is largest for Greece at 11.6%. Next is Ireland at 6.6%, then Portugal at 5.5%. Spain comes next at 3.4%, Italy at 2.0%, the Netherlands at 0.5%, and Belgium at 0.4%. Having a high r - g doesn't automatically mean that the debt dynamics collapse, but rather underscores just how difficult a task it will be for the eurozone periphery to avoid that collapse by having to run bigger and bigger primary surpluses. We have long argued that the first round of budget cuts are often the easiest, with subsequent ones getting more and more difficult given slow growth as well as rising popular opposition to even more austerity.