The uncertainties of schedules and frequency of strike action gradually disappeared in the 1990s, but the occasional wrinkle still needs to be ironed out.
Before the 1990s, strikes were all but unheard of.
mnli hypothesis: Before the 1990s, strikes were all but unheard of. premise: The uncertainties of schedules and frequency of strike action gradually disappeared in the 1990s, but the occasional wrinkle still needs to be ironed out.