Originally Posted by number287
(Despite) its cultural importance, the Daily Gazette (lost) 70 percent of its subscribers since 1920 and, by 1955, (was loosing) (as much as) $ 200,000 a year. (no error).
"Since" triggers the present perfect. The present perfect tense is used to express something that has started in the past and ended in the present. Change "lost" to "has lost."
As the sentence reads, "lost" is in the simple past. The simple past cannot be used to express a continuous action - e.g. the loss of subscribers from 1920 to 1955.