  Sovereign debt ratings provided by rating agencies measure the solvency of a
country, as gauged by a lender or an investor. It is an indication of the risk
involved in investment, and should be determined correctly and in a well timed
manner. The present study reconstructs sovereign debt ratings through logical
analysis of data, which is based on the theory of Boolean functions. It
organizes groups of countries according to twenty World Bank defined variables
for the period 2012 till 2015. The Fitch Rating Agency, one of the three big
global rating agencies, is used as a case study. An approximate algorithm was
crucial in exploring the rating method, in correcting the agencys errors, and
in determining the estimated rating of otherwise non rated countries. The
outcome was a decision tree for each year. Each country was assigned a rating.
On average, the algorithm reached almost ninety eight percentage matched
ratings in the training set, and was verified by eighty four percentage in the
test set. This was a considerable achievement.
