(170217) -- CHICAGO, Feb. 17, 2017 (Xinhua) -- People holding postcards participate in a protest to demonstrate how important immigrants are to America's economy on the Day Without Immigrants at Union Park of Chicago, the United States, Feb. 16, 2017.(Xinhua/Wang Ping) (zhf)more(170217) -- CHICAGO, Feb. 17, 2017 (Xinhua) -- A woman shouts slogans during a protest to demonstrate how important immigrants are to America's economy on the Day Without Immigrants at Union Park of Chicago, the United States, Feb. 16, 2017.(Xinhua/Wang Ping) (zhf)more