Ergodic theory usually has several papers in Annals and Inventiones each year, and is regularly mentioned when the work of recent Fields medalists is described (e.g. Avila, Lindenstrauss, Mirzakhani) but I would estimate the number of ergodic theorists who contribute regularly to MathOverflow as being below ten. MathOverflow has issued three bronze badges for answers to ergodic theory questions, and no silver badges.

Ergodic theory usually has several papers in Annals and Inventiones each year, and is regularly mentioned when the work of recent Fields medalists is described (e.g. Avila, Lindenstrauss, Mirzakhani) but I think that there are no more than ten ergodic theorists who contribute regularly to MathOverflow.

Here is a nice statistic: since MathOverflow opened, there have been as many Fields Medals awarded to researchers active in ergodic theory as there have been bronze tag badges issued for answering ergodic theory questions on MathOverflow. Based on current rates of progress, the first silver tag badge for ergodic theory will be awarded to Anthony Quas at some point in the spring of 2022.