Argentine Tango Radio had 232,000 listeners in January, 2017. Here is a growth chart starting with the launch of the radio in 2015:
Audience growth is quite consistent; I don't know where the ceiling is (I venture that as data packages get cheaper more people will choose to stream music online), but directory listings of all shoutcast compatible streams indicate that Argentine Tango Radio is the largest online-only tango radio worldwide for a while now, so growth can only come from an increasing number of people listening tango music online.
Calculation of number of listeners is based on access count and hence it's a lower estimate. One "listener" may be several people - I know of several practicas, tango classes, and cafes that stream Argentine Tango Radio. All these show up as single listeners in the tally, even though multiple people listen to them.
From an advertising perspective a more important piece of information may be the total listening hours, which was 67,000 hours for January. Here is a historical growth chart for total listening hours:
Finally the growth chart for the number of individual listeners:
(All charts are calculated from proper monthly averages projected to 30 days to exclude fluctuation due to the varying number of days in different months.)
Enjoy listening to ArgentineTangoRadio.com!