I used World Bank data to see which countries contributed most to global external debt in the 2010s. The raw file was messy, so I cleaned it: standardized column names, reshaped years into a tidy format, removed non-country aggregates, and handled missing values. I then summarized totals with dplyr, plotted the top contributors with ggplot2, and printed two short takeaways. For NYU Stern's MSQM 2025