According to a report by Reuters, industry experts have raised fears that shorter-term contracts could eventually push the price of coal up in the U.S. due to decreased production, a result of dwindling infrastructure investment.

In the past coal producers traditionally signed contracts on average of 10-years, now the trend has moved to one to two year contracts.

“Without the financial certainty that comes with long-term supply contracts, coal producers are less willing to undertake expensive new production projects, but with prices rising, companies are not yet worried,” Reuters reported.

"We have not been too reluctant to sign shorter contracts because at least for the next few years we believe prices will increase. Obviously that doesn't make for an easy commitment (to production expansion) for greenfield or existing capacity," director of investor relations at Massey Energy Katharine Kenny told Reuters.