[Gravityloss]

The following contains simplifications.

The shipping sector is squeezed by regulations and fuel prices. If you burn a tonne per hour and it costs a thousand bucks, thats about 8 million bucks per year. If oil price goes up, shipping gets more expensive. Those with newer more efficient or alternative fuel using ships get hit less.

If oil price goes down, it is the opposite.

Regulations need to be predictable. Ship building projects take a long time. If you can be sure that your fuel costs will be high in the future, an investment in better efficiency will pay itself back in a shorter time.