Markets were fired up last week after the United States and Mexico agreed on new trade rules. The Standard & Poor's 500 (S&P 500) Index reached an all-time high and finished the month of August up about 3 percent, reported Michael Sheetz, Thomas Franck, and Alexandra Gibbs of CNBC.

During the latter half of last week, though, the S&P 500 gave back some gains. A hitch in the giddy-up of trade talks between the United States and Canada caused the index to stumble. Damian Paletta, Jeff Stein, and Heather Long of The Washington Post explained:

"High-stakes trade negotiations between the White House and Canadian leaders unraveled Friday, a major setback in President Trump's effort to redraw the North American Free Trade Agreement…the United States and Canada have interwoven economies, with integrated supply chains and vast amounts of trade. The value of goods and services sold between the two countries last year reached $673.1 billion, making Canada the United States' largest export market for goods."

The United States exported about $341 billion of goods and services to Canada in 2017, according to The Office of the U.S. Trade Representative website. Our top exports to Canada during 2017 included:

• Services ($58 billion)
• Vehicles ($52 billion)
• Machinery ($43 billion)
• Electrical machinery ($25 billion)
• Agricultural products ($24 billion)
• Mineral fuels ($20 billion)
• Plastics ($13 billion)

Trade talks are expected to resume next week.