secular
adj.— «In Wall Street parlance, a very long period of falling or, at best, sideways-moving stock prices is termed a “secular” bear market. And there have been some doozies in relatively recent U.S. history.» —“What to do if stocks’ troubles go on…and on” by Tom Petruno Los Angeles Times (California) June 28, 2008. (source: Double-Tongued Dictionary)
Further reading
Enthusiastic book recommendations! Martha’s savoring the biography of Alexander von Humboldt, the 19th-century explorer, polymath, and naturalist who revolutionized our understanding of nature and predicted the effects of human activity on...
You know that Yogi Berra quote about how Nobody ever comes here; it’s too crowded? Actually, the first person to use this was actress Suzanne Ridgeway, who appeared in several movies with The Three Stooges. A new book shows that many well...
I believe this is just OED sense 8 of secular:
“Econ. and Statistics. Of a fluctuation or trend: occurring or persisting over an unlimited period; not periodic or short-term.”