Variously throughout the war, serious shortage of able-bodied men ("manpower") occurred in the country, and women were required to take on many of the traditional male roles, particularly in the area of arms manufacture; though this was only significant in the later years of the war, since unemployed men were often prioritised by employers.[8] Women both found work in the munitions factories (as "munitionettes") despite initial trade union opposition, which directly helped the war effort, but also in the Civil Service, where they took men's jobs, releasing them for the front. The number of women employed by the service increased from 33,000 in 1911 to over 102,000 by 1921.[129] The overall increase in female employment is estimated at 1.4 million, from 5.9 to 7.3 million,[8] and female trade union membership increased from 357,000 in 1914 to over a million by 1918—an increase of 160 percent.[129] Beckett suggests that most of these were working class women going into work at a younger age than they would otherwise have done, or married women returning to work.[8] This taken together with the fact that only 23 percent of women in the munitions industry were actually doing men's jobs, would limit substantially the overall impact of the war on the long-term prospects of the working woman.[8]