America's stock market is shrinking. The number of public companies has been cut roughly in half over the past two decades, mostly by choice.

Some don't want to deal with the pressure and reporting requirements. Others are avoiding the hassle and expense of an IPO. And a lucky few just don't need the money.
 
Now, the New York Stock Exchange is trying to lure more companies back to the public market, even if it involves taking a less traveled route.
 
Last year, Spotify (SPOT) went public on the NYSE in a most unconventional way: through a direct listing. It didn't hire underwriters from Wall Street investment banks, and no new shares were issued to raise money. Yet Spotify became a public company with a valuation at the time of nearly $30 billion.
 
Slack (WORK), the workplace communication tool, also decided to forgo the traditional initial public offering route. In June, it also pulled off a direct listing on the NYSE, achieving a valuation north of $20 billion. And it didn't hire underwriters or raise any new capital, either.
 
The NYSE is now trying to persuade more unicorns to follow in the footsteps of those outliers, but with a twist.The exchange filed paperwork earlier this week with the Securities and Exchange Commission proposing rule changes to allow direct listings to raise money by issuing new shares to the public.
 
"We think companies should go public. We want to create as many pathways as possible to help achieve that goal," John Tuttle, NYSE's vice chairman, told CNN Business.
 
Direct listings have their skeptics, but Tuttle said "a lot" of companies from various industries are considering the same route as Spotify and Slack.
 
"In response to the demands of the marketplace, we are working to evolve our offering," Tuttle said.
The SEC declined comment on the proposal, which the agency must approve before it can take effect. Tuttle expects the approval process to take at least 90 days.