In complex systems, the slightest variation in initial conditions can create largedeviations in future system conditions over time and not necessarily in predictable ways.
Varadhan, New York University, for his work in probability theory, especially his work on largedeviations from expected random behavior which has revolutionized this field of study during the second half of the 20th century, and become a cornerstone of both pure and applied probability.
Since small deviations are common and large ones are rare, the result of plotting data in this way is a curve shaped somewhat like the cross-section of a bell.