There is a rice field in Xiaofu Village. The year before last, 4 tons of rice were harvested. Last year, due to floods, only 3.2 tons of rice were harvested. What percentage was the reduction in production last year compared to the previous year?
小富村有一块水稻田，前年共收水稻4吨，去年由于遭受水灾，只收水稻3.2吨．去年比前年减产了百分之几？
<gadget id="calculator">4 - 3.2</gadget>
<output>0.8</output>

<gadget id="calculator">0.8 / 4</gadget>
<output>0.2</output>

<result>0.2</result>