Is this more or less concentrated than other industries? I feel like tech is a lot more consolidated than the maritime industry, for example.

100 firms is not a concentrated industry according to any economist’a definitions.

However, this is a group of 100 or so firms in terms of “revenue extracted from the ocean by these firms as a percentage of the total”. That is not a useful market definition. These firms are mostly not competitors (some subsets of them are in their separate markets!).

Laying communications cable, shipping, fishing and oil and gas extraction are just four of the listed industries on this list of 100 companies.

These four separate industries may be concentrated or not but this article doesn’t tell you one way or the other.

(Source: Industrial Organization economist.)

The article itself mentions:

"This extreme concentration of revenue in the ocean economy mirrors the structure of the global economy as a whole. For many land-based industries, a relatively small number of transnational corporations control a huge market share of output."

But I agree with you re: tech -- this ocean economy is way less concentrated than search engines or social networks.

Could you give an overview of the maritime industry in this respect? Not my (HN’s?) area of expertise. :)

The article has some good examples:

“The volume of goods transported by container shipping each year has quadrupled since 2000, and about 600,000 submarine cables have been laid on the seafloor in that time, which now carry almost all international telecommunications. The energy generated by offshore wind farms has increased 400-fold in the past two decades, and the volume of farmed seafood has grown by five percent on average each year.

During the same time period, most major discoveries of oil and gas deposits have been made offshore and around 500,000 square miles of the seabed has been leased for exploratory mining. There was practically no marine biotechnology sector at the turn of the millennium, but since then, more than 13,000 marine genetic sequences have been patented.

...

In 2018, the 100 largest companies took an estimated 60 percent of all revenues in eight industries: offshore oil and gas, container shipping companies carrying many of the goods we buy, companies producing and processing seafood, offshore wind energy producers, cruise tourism operators, and a number of industries that support the wider ocean economy, including marine parts and equipment makers, shipbuilders and repairers, and port maintenance businesses.”