Historian Niall Ferguson proposed that LTCM's collapse stemmed in part from their use of only five years of financial data to prepare their mathematical models, thus drastically under-estimating the risks of a profound economic crisis. Using ten years of data would have included the 1987 US market crash, while using 80 years of data would have included many minor and major economic downturns including the 1918 Russian sovereign debt default after the First World War and Russian Civil War, highlighting the possibility of a major foreign event causing international repercussions that LTCM seemingly overlooked.