Both, depending on the company. The great companies are play heavily in the futures market, as a result their production is mostly locked up when the boom comes and so they don't make any extra money. The not so great companies sell to market mostly, and make a ton of profit in the boom years and are lucky if they don't go bankrupt in the bust years.
Of course great and not so great are by my definition of great. You can do should do your own investigation.
Of course great and not so great are by my definition of great. You can do should do your own investigation.