One way to measure the strength of the stock market is the vitality of Initial Public Offerings (IPOs). Quality, quantity, performance.
Quantity: although the 3rd quarter was a quiet one, 2017 overall has seen more action than 2016. Several big names such as Spotify and Dropbox may go public later this year, which would give the IPO market a lift.
Quality/Performance: the average IPO in the 3rd quarter of 2017 gained 36%. This was entirely due to strong results from biotechs.
Overall, the IPO market will never be like it was twenty years ago. The markets have changed and companies have other routes for funding than the heavily regulated public markets.