03-013 · EVIDENCE B · LOW-RISK READING
Do not work more than 49 hours per week
别把每周工作时间一味往上加：过了 49 小时上下，多干一小时多出的活越来越少
You might earn less in overtime pay. You may also need to put in effort to negotiate with your supervisor.
Records from British munitions factories during World War I show that when workers kept weekly hours under 49, output rose in direct proportion to the time spent working. Once they exceeded 49 hours, the growth rate began to drop. Output from workers putting in 70 hours per week was practically identical to that of those working 56 hours — those extra 14 hours yielded no additional results. In total, this data covers a period spanning 100 years.
B
Move “Do not work more than 49 hours per week” to Future Me's calendar
The excuse
Future Me has a clearer calendar, more patience, and apparently the same responsibilities.
What feels good now
Today I keep a little money, a few minutes, a bit of persistence and avoid interrupting my default routine.
What the source says
The source summarizes the return this way: “Records from British munitions factories during World War I show that when workers kept weekly hours under 49, output rose in direct proportion to the time spent working. Once they exceeded 49 hours, the growth rate began to drop. Output from workers putting in 70 hours per week was practically identical to that of those working 56 hours — those extra 14 hours yielded no additional results. In total, this data covers a period spanning 100 years.” Evidence grade B. The original states the population, caveats, and sources; this is not a personal forecast.
Open the original entry, check who the evidence applies to, then pick one small step that fits.
THE ENGLISH EDITION
Original recommendation and evidence
13. Do not work more than 49 hours per week
Cost: You might earn less in overtime pay. You may also need to put in effort to negotiate with your supervisor.
In plain terms: Records from British munitions factories during World War I show that when workers kept weekly hours under 49, output rose in direct proportion to the time spent working. Once they exceeded 49 hours, the growth rate began to drop. Output from workers putting in 70 hours per week was practically identical to that of those working 56 hours — those extra 14 hours yielded no additional results. In total, this data covers a period spanning 100 years.
Benefit: Data from British munitions factories in World War I demonstrates that output rises steadily with working hours up to 49 per week. After that threshold, the rate of growth slows. Peak output is reached at roughly 63 hours. At 70 hours, output remains essentially the same as at 56 hours, meaning those extra 14 hours are wasted effort.
Evidence grade: B
Sources: Pencavel (2015). The Productivity of Working Hours. The Economic Journal. <https://doi.org/10.1111/ecoj.12166>
Notes: These figures come from factories a century ago where most workers were women performing manual labor. This threshold may differ for cognitive work; the authors themselves note that other occupations could have higher or lower limits. What is reliable, though, is the overall trend: beyond a certain point, adding more hours yields almost no extra output. The specific figure of 49 hours is not proven.
Read the complete Chinese source and notes
13. 别把每周工作时间一味往上加：过了 49 小时上下，多干一小时多出的活越来越少
成本: 可能少拿一些加班费。也可能要花力气和上级谈。
说人话: 一战时英国军工厂的记录显示，每周干 49 小时以内，干多久就出多少活。超过 49 小时，多干一小时多出的活越来越少。一周干 70 小时和干 56 小时出的活几乎一样，多干的那 14 小时是白干。
收益: 一战时期英国军工厂工人的产出记录：每周 49 小时以内，产出与工时成正比。超过 49 小时，产出的增速开始变慢。大约 63 小时达到最大。干 70 小时的产出与干 56 小时几乎没有差别，多干的 14 小时等于白干。
证据等级: B
来源: Pencavel (2015). The Productivity of Working Hours. The Economic Journal. <https://doi.org/10.1111/ecoj.12166>
备注: 数据来自一百年前的工厂，干的是体力活，工人以女性为主。这道坎搬到脑力工作上不一定一样，作者自己也说别的工种可能更高或更低。可靠的是方向：过了某个点，再多干也几乎不多出活。49 这个具体数字不可靠。
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