The stock market has bounced back strongly this year, but advertising companies aren’t participating in the rebound — a bad sign for publishers and the broader economy.

While the S&P 500 stock index rose 12.3% in the first quarter — the best start to the year since 1998 — the gains were concentrated in handful of industries, such as technology.

The stocks of advertising giants like Interpublic, Omnicom, Publicis and WPP didn’t keep pace with that bounce-back or have declined this year. That’s a worrisome sign; the health of ad agencies reflects trends for major industries, like automotive, finance, retail and telecom.

Even more concerning, the gains weren’t based on signs of underlying strength in most businesses. Instead, the Federal Reserve basically pledged to stop raising interest rates, making it easier for publicly traded companies to borrow more money to plow into stock buybacks.

As much as President Trump likes to boast about the strong economy and an unemployment rate that’s near 50-year lows, his public demands that the Fed either cut rates or return to crisis-era quantitative easing don’t inspire confidence. The Fed will shrug off those pleas — making it harder for Trump to get re-elected during a long overdue recession.

Instead, the Fed's policy committee will pay attention to the stock market for cues on what to do next.

Unfortunately, Wall Street analysts are still drastically cutting their earnings estimates for 2019. The consensus estimate for S&P 500 earnings per share has fallen about 7% since last summer to about $165 currently.

Stocks may rise, but they will be more expensive, compared with their diminished earnings power if those forecasts are realized.

Earnings estimates almost always decline during any calendar year as companies provide more realistic guidance of future profits. But this year’s plunge in estimates is the steepest since 2015.  The deep drop in earnings estimates that year forewarned of a stock market drop that finally bottomed out in February 2016.

The Fed may end up cutting interest rates later this year, but the central bank’s power to stimulate growth has weakened over the years. Everyone who could refinance their debt at lower rates probably already has, leaving little else to goose consumer spending power.