How do I interpret changes in countries estimates over time?
A change over time could be attributed to 4 factors. First of all, it could come from a change in the score assigned to a country by the same source over time. This is the most common and relevant factor, directly reflecting changes in perceptions of the country’s performance. A second factor is the addition of new sources whose ratings might be different from the average ratings from pre-existing sources. Changes over time in relative performance may also reflect the addition of new countries to the aggregate indicator. If for example we add a country with a governance rating that is high relative to those countries already in the index, then by construction all the countries which rank lower than this country will receive lower scores. Finally, a change in a country’s performance could derive from a change in the weights in the aggregation procedure. Overall, however, these last two factors typically have only very small effects on changes. The first factor is by far the most relevan
