PORTLAND, Ore. — The 2020 U.S. census will take a closer look at the racial make-up of America — asking for even more specifics about ethnicity. For one racial group in the Pacific Northwest, the census offers a chance to build on the success of the last go-round — a survey that showed a surprising result when it came to the fastest growing population in Portland. “For a long time, a lot of people thought that the Asian and Hispanic populations have been the fastest growing within the city of Portland,” said Nick Chun, a demographer at Portland State University.