> The researchers analyzed US-flagged ships less than 1,000 gross tonnage, which includes primarily passenger ships and three types of tugboats.
This is the buried lede. They are excluding basically all cargo shipping.
- Very little of the shipping industry is US-flagged. Most commercial ships sail under flags of convenience such as Panama and Libera, because of their reduced regulations and costs.
- Nobody carries cargo any distance in vessels of less than 1000 gross tons, because that scale would be uneconomical to operate. Modern seagoing cargo ships have about one crew member per 8000 tons of cargo.
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