Speculators in small stocks hunt for fabled “tenbaggers” that soar tenfold in price. But the real killing is made from unlisted companies that deliver returns of 100 to 200 times.

Speech and text-recognition star Appen is an example. Private-equity firm Anacacia Capital and Appen management invested in it in a 2009 capital raising at less than 10¢ a share. Appen listed on the ASX in 2015 at 50¢ and trades above $23.