Several years ago, before I’d published any of my books, I read Charles Stross’s essays on the publishing industry.

His essay on writing income, in particular, was quite discouraging to a new would-be writer. 
My favorite author, a good mid-list author, could just barely scrap by on his writing income. And it turned out the writers have the highest income inequality of nearly all professions. He quotes from a research article “The top 10% of authors earn more than 50% of total income, while the bottom 50% earn less than 10% of total income.”

Fast forward a few years. While the economics of the traditional publishing industry has stayed much the same, the economics of the indie publishing industry are very different. 
The ratio of inequality may still exist, as there are many people self-publishing, but in terms of absolute terms: the number of writers capable of being supported by writing as a full time career has grown.
Here’s why:
A Bigger Bite of Pie
Self-published authors get a bigger bite of piece with every book sold. The exact figures seem to vary, but on average, traditionally published authors get about 60 cents for every book sold.
By comparison, when selling indie-published ebooks at $2.99 (a common price point, and the medium that self-published authors tend to sell the most in — see my essay on pricing), authors get about $2.00 per book. 
A traditionally published author would need to sell 125,000 books to earn a $75,000 income, while a self-published author could earn the same income selling 37,500 books.

More Slices
The number of books many readers buy is limited to a portion of their disposable income. At $10 each, traditionally published books are expensive.
With the exception of non-fiction books that address a niche topic, most books are fungible. That is, a reader wants to read a book they’ll love in genre X, and any of thousands of different books will fulfill that need. (I differ from Stross in this regard, as he says books are non-fungible.)
If a reader who is budget limited can buy indie-published books at $2.99 as compared to traditionally published books $9.99, they will buy more of the less expensive books. 
They can afford to buy 3 times as many, therefore, the total number of books purchased is greater.
Not all readers are budget limited, but if we assume that half are, then we’re floating the entire book market by 50%.
Since the indie-author’s royalty per book is higher, and their books are priced such that readers can afford to buy more books, the total royalties available to indie writers are about 4 1/2 times greater than that available to traditionally published authors.
Even if indie authors are subject to the same income inequity as their traditionally published brethren,  the economics will still support five times as many writers being supported by writing indie books.
If the income inequity is better or worse, then this difference will be magnified or diminished. Also, to be fair, we should realize that the traditional publishing industry supports a great many jobs (editors, proofers, designers) that don’t exist or are greatly diminished in the indie portion of the field. So we can’t look at it and say the indie movement is growing jobs as a whole, merely that it’s growing writers as a portion of that industry.
If you dream of being a full-time writer, it’s never been a better time to do it.