NEW YORK (Bloomberg) — Bermuda-based Nabors Industries Ltd., the world's largest onshore oil and natural-gas driller, fell 16 percent in New York trading on Monday after analysts from two firms cut the stock's rating.

Nabors, which has corporate offices in Houston, tumbled $2.34 to $12.16 in New York Stock Exchange composite trading on Monday and yesterday it dropped another six cents. The stock has dropped 56 percent this year.

Merrill Lynch & Co. cut its rating to "underperform" from "buy". Bill Herbert, an analyst at Simmons & Co. in Houston, lowered his rating to "underweight" from "overweight".

"Specifically our concern relates to management compensation which has been far too self-serving and excessive for too long," Herbert wrote on Monday in a note to investors. "We continued to be troubled by management's lack of judgment on this issue as well as the board's mystifying quiescence with respect to management compensation."