Central Bank Balance Sheets: Expansion and Reduction since 1900. Niall Ferguson, May 2014, Paper. "In this paper we study the evolution of central banks’ balance sheets in twelve advanced economies since 1900. We present a new dataset assembled from a wide array of historical sources. We find that balance sheet size in most developed countries has fluctuated within rather clearly defined bands relative to output. Historically, clusters of big expansions and contractions of balance sheets have been associated with periods of geopolitical or financial crisis. This explains the co-movement between the size of central bank balance sheets and public debt levels in the past century..."