Complex sentence: Originally, a national strike required a two-thirds majority in a ballot of members but proved near impossible to achieve and the majority was reduced to 55% in 1970 and to 50% in 1984.
Split into simpler sentences: Originally, a national strike required a two-thirds majority in a ballot of members. This proved near impossible to achieve and the majority was reduced to 55% in 1970 and then to 50% in 1984.