In this article, the development of the yield of the polyolefin sector as well as of the individual companies was investigated without differentiation in products or market segments. The main driving factors were identified using as source of information the annual reports of 19 international polyolefin producing companies (resp. Business units) in the period from 1986 through 1997. It was found out that the polyolefin sector is characterized by a cyclical development of the yield. This cyclicality is caused by cyclical variations in demand for end products. it is further intensified by the procyclical investment behavior of the majority of the market participants. In addition, it was observed that the individual investment pattern has a significant impact on the average Return on Capital Employed (ROCE) of polyolefin producers during a market cycle. Companies with a long-term investment strategy which is in line with the average growth of demand for polyolefin products have a significantly higher return than companies with a procyclical investment behavior.