Editing Shift work (section)

=== Shift system ===
The 42-hour work-week allows for the most even distribution of work time. A 3:1 ratio of work days to days off is most effective for eight-hour shifts, and a 2:2 ratio of work days to days off is most effective for twelve-hour shifts.<ref>{{cite journal | last1 = Knauth | first1 = P | last2 = Rohmert | first2 = W | last3 = Rutenfranz | first3 = J | title = Systematic selection of shift plans for continuous production with the aid of work-physiological criteria | journal = Applied Ergonomics | date=March 1979 | volume = 10 | issue = 1 | pages = 9–15 | doi=10.1016/0003-6870(79)90003-6| pmid = 15676345 }}</ref><ref>{{cite journal | last1 = Rutenfranz | first1 = J | last2 = Knauth | first2 = P | last3 = Colquhoun | first3 = W | title = Hours of work and shiftwork | journal = Ergonomics | date=May 1976 | volume = 19 | issue = 3 | pages = 331–340 | doi=10.1080/00140137608931549| pmid = 976239 }}</ref> Eight-hour shifts and twelve-hour shifts are common in manufacturing and health care. Twelve-hour shifts are also used with a very slow rotation in the [[petroleum industry]]. Twenty-four-hour shifts are common in health care and emergency services.<ref name=":2" />