Perhaps is not well translated. Here they called it "Impuesto por Ganancias inesperadas",
It seems that when you have an exceptional rise of the price of your crop, due to unexpected reasons (i.e. a shortage of corn or soybeans) you have to pay a tax on the difference between the initial price of the projected crop and the current price of the crop when you have this in your warehouse.
Therefore if you are lucky, you deserves punishment. Is the institution of the ENVY, a capital sin which can be defined as the sadness for the alien's fortune. (tristeza del bien ajeno).
Perhaps you are not familiar with this, but this is common now and you will hear and read this in the forthcoming news.
I suspect this is the reason. 
