By Dick - 28 Jan 2020
I really fun, creative, and interesting use of albatrosses (https://www.nytimes.com/2020/01/27/science/albatross-ocean-radar.html)
has collected data suggesting that far fewer vessels are using their AIS than I would have predicted. Data is still coming in and only certain international waters have been surveyed, but about 1/3rd of vessels in these areas appear to have their AIS turned off.
I doubt this is the case near big western commercial areas such as the UK and the Atlantic coastal waters of the US, but open water might be a different story. A bit sobering for those who feel AIS was a big boost to safety at sea.
My best, Dick Stevenson, s/v Alchemy