Found this study on biz av apparently focusing on Europe. It's 147 pages long so I sure didn't read it all but pulled a couple of statements that might be of interest. This statement generally applies to Europe. Inexperienced pilots don't remain inexperienced:
"Whereas less experienced pilots seem to be plentiful in the market, the labour supply for experienced pilots is rather tight.
Most operators in Business Aviation do not see a major workforce shortage today, but forecast possible shortages in the mid-to long-term."
This from Section 10.4.1 addresses US biz av sector:
"Since only around 20% of the total pilot workforce in the US is employed in Business Aviation, this equates to approximately 1070 new pilots joining Business Aviation per year.
Those interviewed for the study reported no current shortage of pilots in the US Business Aviation sector.
However, the difficulties regional airlines face in hiring entry-level pilots could point to a problem for the future supply of pilots for Business Aviation."
http://www.ebaa.org/documents/docume..._skills_ba.pdf