Script computation.m allows for computing the average spread over riskless (German) bonds. It also plots the
 Kernel density of the observed mean debt levels and computes the regression coefficient associated with the relationchip between
GDP levels and debt levels. It uses data from files:
1) OECD_10Y_gov_bond_yields_2009_2019.xls
2) OECD_GDP_ppp_per_capita_in_2015_dollars_09_19.xls
3) Mean debt levels between 2009 2019.xlsx

The remaining xls/xlsx files contain raw data used for preparing spreadsheets 1),2),3)

Note: Latvia, Lithuania, Luxembourg, Estonia were removed because of (partial) unavailability of yields data. Data come from the OECD database.