The bull market is turning 4 years old — but yields could crash the party

This bull market has now run for four years, and throughout that stretch technology stocks have served as the default answer to nearly every question investors asked about where growth would come from. That leadership has shaped index returns, portfolio allocations, and the broader narrative around what is driving equity prices higher.

The complication is the bond market. When yields move sharply, they change the calculus for equities — particularly for growth-oriented technology names whose valuations depend heavily on future earnings discounted back to the present. Rising yields can pressure those valuations; falling yields can support them, but may also signal softer economic expectations. Either direction can matter, and neither is automatically good or bad for stocks in general.

For observers, the key question is whether technology leadership can persist if yields become volatile. Watch how rate-sensitive sectors behave relative to the broader market, and whether any shift in leadership is broad or narrow. A four-year-old bull market is not inherently fragile, but it does mean the drivers of returns deserve closer attention than they did earlier in the cycle.