Declines and losses are scary. If Black Friday produces fewer shoppers than last year, or visitor numbers dwindle at a regional attraction during tourist season, people start fretting about what that means. That may not be true at Umpqua Community College. Following a 43 percent hike in enrollment between the 2007-08 and 2010-11 academic years, the college is reporting a depletion in the student population. Last year, the decrease was 7 percent. This fall, enrollment dropped by 20 percent. It’s a drop that’s gaining momentum. Yet it’s not entirely out of line with what’s happening at other two-year colleges in …