For the first time, China has replaced Canada as the United States’ largest trading partner.

According to the latest numbers from the U.S. Census Bureau, in the first nine months of this year, the value of imports and exports between the U.S. and China was US$441.6 billion. The U.S.- Canada trade relationship, meanwhile, was worth slightly less, at $438.1 billion.

But the reason behind the shift in numbers has less to do with trade volumes and more to do with falling oil prices.

The price of crude oil – which makes up the vast majority of Canadian exports to the U.S. -- has plummeted. So far in 2015, that’s helped send the value of Canada’s trade with the U.S. down almost 12 per cent from the same time last year, from $495 billion to approximately $438 billion.

And yet, the U.S. continues to buy large amounts of Canadian oil. It imported 101.3 million barrels of crude from Canada in September, according to the Census Bureau numbers -- the most this year.