The stock market bull run is in its 'twilight', Fidelity's global macro head says

• Despite a flat start to September, the S&P 500 index is still boasting impressive year-to-date gains.
• The benchmark stock-market gauge is up by over 16% so far in 2023, but one expert sees the rally losing steam.
• The secular bull market for equities is in its "twilight", according to Fidelity Investments' global macro head Jurrien Timmer.

A surge in artificial intelligence-related tech shares has buoyed the stock market this year, in spite of the Federal Reserve's most aggressive monetary-tightening campaign since the 1980s. 

But one expert believes the rally is close to petering out, as rising bond yields erode the appeal of equities.