More negative economic data coming out in the U.S. on Tuesday highlights the spread of the financial industry crisis to the real economy, says RBC Capital Markets.

In a research note, the firm reports that the CaseShiller house price index for July showed a worse-than-expected 16.3% decline year-over-year. And 14 of the 20 metropolitan areas recorded monthly declines, and prices dropped for all 20 metro areas on a year-over-year basis (led by an almost 30% decline in Las Vegas).

“No relief is in sight for homeowners,” RBC says. “The negative wealth impact is being compounded by the hits to consumers’ equity portfolios. Combined with continued high energy prices and declining access to credit, the consumer is under siege.”

That observation is backed up by the latest U.S. weekly same-store sales, which moderated to just 1.1% year-over-year growth in the week of Sept. 30, the fifth-lowest rate since 2003. “The data are providing evidence that economic growth is slowing and that the Wall Street crisis is spreading to the real economy,” RBC says.

“The Wall Street crisis is likely to continue and the collateral damage to the real economy is likely to rise. These developments suggest significant downside risks for the economy on top of the moderation we had already expected for growth during the second half of 2008,” the report concludes.

The news out of Canada is a bit brighter, as gross domestic product came in much stronger than expected in July, rising 0.7% following the 0.1% gain in June. Expectations had been for a more moderate 0.2% rise, RBC reports.

“The increase in July GDP bodes well for economic growth to remain in the positive column in the third quarter after eking out a meagre 0.3% annualized gain in the second quarter and declining 0.8% in the first. In fact, this report reinforces our expectation of a third-quarter gain of 2.5%,” RBC says.

“However, with the deterioration in financial markets indicating no easing in the cost of capital, which is weighing on both the U.S. and Canadian economies, the third quarter could well represent the peak in growth in Canada this year,” it adds.

“This growing downside risk to GDP is increasingly countering earlier-expressed concerns by the Bank of Canada about the upside risks to inflation,” it says. “Our forecast assumes that in this environment the current, and still stimulative, 3% overnight rate will be maintained near-term. However, there is the growing risk of a near-term cut if the credit tightening that has set in following the setback to the U.S. government’s financial market rescue plan does not materially abate.”