The x-axis shows the five years before and after a country ratified the CAT. Year 0 is the year that the country ratified the CAT. For example, year 0 for the United States was 1994, while year 0 for Nicaragua was 2005. The line shows the average torture score for countries during the five years leading up to ratification and the five years following ratification (where 0 refers to frequent torture and 2 refers to no torture). If the average country had reduced torture during this period, then the line would have sloped up.  The data source is Cingranelli-Richards.