IMF researchers S. M. Ali Abbas, Nazim Belhocine, Asmaa El-Ganainy, and Mark Horton are trying to make the task of studying debt cycles and debt sustainability easier.  They have begun building a database of historical public debt.  At VoxEU, they have posted a series of interesting graphs from the data they have compiled so far.  Including this one, that they say provides an "historical perspective of debt developments in advanced, emerging, and low-income economies. Debt levels in advanced economies (now the G20) averaged 55% of GDP over 1880–2009, with a number of peaks and troughs that correspond with key historical events along the way.":

Here is what the authors say about the value of this data moving forward:

The composition of the 11 debt reductions observed during 1880–1914, the first era of financial globalisation, is quite similar to that witnessed in the post-1970 financially liberalised period. In both cases, the debt ratio reductions were mainly caused by large primary surpluses. In fact, the post-1970s debt reductions are accounted for almost entirely by primary surplus improvements. However, insofar as such improvements are boosted by the cycle and easier to implement in the context of strong growth, these results may somewhat understate the true role of growth in debt declines; strong growth was a consistent feature of most debt decline episodes.2 That conventional fiscal adjustment and growth have led the way in periods of global financial integration is intuitive as well as consistent with previous studies (such as IMF 2010).

Looking ahead, highly indebted advanced economies are confronted by a challenging landscape. The pursuit of unconventional options – such as reverting to financial repression policies akin to those taken during the post-WWII years, reducing the burden of domestic debt through higher inflation, or restructuring – may be a temptingshortcut but it comes with high costs. A gradual but steady adjustment is the right way to go. History shows an orderly adjustment is much easier in the context of sustained medium-term growth. This suggests that there is a premium on both implementing structural measures that improve competitiveness and the business environment, and designing fiscal adjustment in a manner that minimises the drag on growth.

Read Lessons from a century of large public debt reductions and build-ups here.