The road to a Nobel Prize, the most respected scientific award in the world, is growing ever longer, with almost half of winners now waiting more than 20 years from making a Nobel-worthy discovery to receiving the prize. 

One analysis shows that the average time between publishing the work and receiving one of the science prizes has nearly doubled in the past 60 years. Across the three science prizes, chemistry now has the longest "Nobel lag"-an average of 30 years over the past decade -and physiology or medicine has the shortest, at 26 years.

Alfred Nobel's will stated that the prizes should be awarded "to those who, during the previous year, shall have given the greatest benefit to mankind. "In reality this has only happened a few times. But in the first half of the twentieth century, it was common for Nobel prize winners to be in their 30s -and that is unheard of now, says Santo Fortunato, now a computational social scientist at Indiana University.

There are a number of possible reasons for this, says Yian Yin, a computational social scientist at Comell University. It could be that the overall number of breakthroughs is increasing each year, so awards cannot keep up with the number of people who deserve to be recognized, he says. It is also the case that the importance of some works, which Yin describes as "sleeping beauties" are only realized years or decades later. Besides, the lengthening gap could be a sign that there has been a decrease in "disruptive" science -important studies or discoveries that change the paradigm( 范 式 )of their field. This could be causing the Nobel committees to focus more on the past.

Fortunato points out that, if the gap continues to grow, outstanding scientists could miss out on the award owing to the Nobel Committee's rule banning posthumous prizes(追授奖项) . "It has to stop at some point, "he says, adding that a rethink of the posthumous-awarding ban would allow more people's work to get the recognition that it deserves.