NEW YORK ( TheStreet) -- Two economic theories I track could be in sync as October begins by providing dual warnings that the global economy is weakening, and that the stock market is vulnerable.Dow Theory is now providing a tug-of-war with industrials near multi-year highs while transports are negative on monthly, weekly and daily charts. In the Tech Age the more modern theory involves the leadership from semiconductors as almost every product made has a chip as a component, and recently there have been warnings that the demand for chips is weakening. Last week earnings warnings from FedEx ( FDX) and Norfolk Southern ( NSC) caused the entire transportation sector to swoon. Last week industrials were down just 13 points, while transports were down 305 points for a weekly loss of 5.8%. This had Dow Theorists scratching their heads as industrials set a new year-to-date closing high, while transports were closer its year-to-date low of 4847.73 set on June 4. The tech-heavy Nasdaq set a new multiyear high last week, and on Monday the PHLX Semiconductor Sector Index, or SOX, broke below both its 50-day and 200-day simple moving averages at 390.76 and 395.58. Without a rebound into Friday, the SOX will have negative monthly, weekly and daily charts.