A trending quantity is a number that is generally increasing or decreasing. When the numbers are steadily decreasing, we have a downward trend, and when the numbers are steadily increasing, we have an upward trend.
On our problem, we have a population growth/decline starting at 2004 until 2009. If we analyze the years individually, it is not perfectly clear if the ternd is downward or upward, however, analyzing the whole table it is possible to see that we have an upward trend. If we compare two distinct points not consecutive of our table, the point closer to 2009 will present a bigger population for most points in our table, which shows a rise on the population value as the years goes by. To see it properly the ideal would be to plot the points and check the slope of the trend line.