The U.S. trade deficit fell in December as exports hit their highest level in more than 1-1/2 years amid record shipments of technology products, but strengthening domestic demand points to further rises in imports, which could constrain economic growth. The trade deficit rose 0.4 percent to a four-year high of $502.3 billion in 2016. President Donald Trump has blamed U.S. trade policy for the loss of American factory jobs and has vowed to make sweeping changes, starting with pulling out of the 12-nation Trans-Pacific Partnership trade pact.