Pick your poison on why to be nervous on the market. 

Fears of a profit-busting trade war that sends market darling Apple (AAPL) down 10%? Check. Rising wage inflation that pounds Walmart's (WMT) bottom line? Check. A more hawkish Federal Reserve that sucks the juice out of high growth stocks such as FANG? Check. Or, how about just a series of leading-edge trends quietly playing out in the market that suggest stocks could soon reverse course to the downside, perhaps severely. 

Long-time market bear David Rosenberg of Gluskin Sheff serves up three trends in the market that the bulls must watch closely. It's buyer beware, or else. 

The Transports Look Weak

Transport stocks are often viewed as a forward indicator on the health of the global economy. Considering the Dow Transports and S&P 500 Transports peaked in the second week of January, and haven't retested those highs, Rosenberg thinks this is a worthy red flag. 

Dow Transports stay stuck in neutral.
Dow Transports stay stuck in neutral.

About Those Banks

Despite the prospect of quicker interest rate hikes this year, which on paper should be good for bank profit margins, the bank stocks aren't acting well. Rosenberg believes this is yet another cause for worry.

Bank stocks continue to act weak.
Bank stocks continue to act weak.

Housing Stocks Not Doing Well

Amid tight supplies of new homes (which is jacking up prices for would-be buyers) and rising interest rates, housing stocks are severely lagging. In fact, Rosenberg points out, housing stocks are in a bear market as defined by a more than 20% pullback from the highs. 

Housing stocks in a bear market.
Housing stocks in a bear market.

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