That means only 10% of worldwide dredging is done in China and US combined, which surprises me. I wonder how much of the total is maintenance versus digging to a certain depth for the first time.

The take away would be there is a lot of the "rest of the world" depending on silty River mouths. China and the US depend on a small number of massive ports and the RoW depends on lots and lots of silty ports.

(The OP notes very early on that that Wikipedia page came into existence four days ago because of the investigations that led to the article.)