A century-old market theory just flashed a rare buy signal, suggesting the three-year-old bull market may still have unfinished business as 2026 gets underway.

In a Monday email note, Adam Turnquist, chief technical strategist at LPL Financial, highlighted that Dow Theory has once again turned bullish.

“A Dow Theory buy signal has been triggered, reinforcing the case that the primary trend for the broader market remains higher,” he said.

The signal rests on a simple but demanding idea.

When industrial stocks and transportation stocks rally together, the broader market trend usually follows.

What Is Dow Theory And Why It Matters

Dow Theory dates back to the early 1900s. It was developed by Charles Dow, co-founder and editor of The Wall Street Journal.

The framework uses two major benchmarks: the Dow Jones Industrial Average and the Dow Jones Transportation Average. The core principle is confirmation.

The logic is intuitive. If industrial firms are producing more goods, transportation companies should see rising demand to ship those goods. When both groups move higher in unison, Dow believed it reflected improving economic conditions and a healthy market trend.

Why ...