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The graph compares the rates of unemployment between the US and Japan from March 1993 to March 1999. Overall, an upward trend in Japan and a downward trend in the US limited a significant difference in the unemployment rate between these two countries.
... Break this into two parts;
The graph compares the rates of unemployment between the US and Japan from March 1993 to March 1999. ... (Introduction)
Overall, an upward trend in Japan and a downward trend in the US limited a significant difference in the unemployment rate between these two countries. ... (Overview)
Then move on to a new para to discuss the details.
Structure - Introduction, Overview, Details