The lowest profitability was recorded in 1999 when prices were at their lowest and the highest profitability was achieved in 1998 when prices were almost at their 5 year high.
A legalacsonyabb jövedelmezőséget 1999-ben érték el, amikor az árak a legalacsonyabbak voltak, a legmagasabbat pedig 1998-ban, amikor az árak megközelítették az ötéves csúcspontjukat.