Here's an interesting chart from informationisbeautiful.net that shows how many units (either physical or digital) an artist has to sell in order to make the minimum wage of $1,160 per month. In other words, this is what you have to sell just to make the same amount as flipping burgers at Micky D's.
There are quite of few of the following numbers that I have a problem with, most notably the album download and retail CD figures (they're lower than they should be), but the general gist of the graphic is correct, which is that you have to sell a massive amount of digital product for it to amount to anything.
Keep in mind that most artists make their income from a combination of all the categories on the chart, so the end result is not quite as dire as the graphic makes it seem.
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