Richardson also applied his mathematical skills in service of his pacifist principles, in particular in understanding the basis of international conflict. For this reason, he is now considered the initiator, or co-initiator (with
Quincy Wright and
Pitirim Sorokin as well as others such as
Kenneth Boulding,
Anatol Rapaport and
Adam Curle), of the scientific analysis of conflict—an interdisciplinary topic of quantitative and mathematical social science dedicated to systematic investigation of the causes of war and conditions of peace. As he had done with weather, he analysed war using mainly differential equations and probability theory. Considering the armament of two nations, Richardson posited an idealised system of equations whereby the rate of a nation's armament buildup is directly proportional to the amount of arms its rival has and also to the grievances felt toward the rival, and inversely proportional to the amount of arms it already has. Solutions of this system of equations yield insightful conclusions about the nature, and the stability or instability, of various hypothetical conditions that might obtain between nations. Richardson also originated the theory that the propensity for war between two nations is a function of the length of their common border. And in
Arms and Insecurity (1949), and
Statistics of Deadly Quarrels (1960), he sought to analyse the causes of war statistically. Factors he assessed included economics, language, and religion. In the preface of the latter, he wrote: "There is in the world a great deal of brilliant, witty political discussion which leads to no settled convictions. My aim has been different: namely to examine a few notions by quantitative techniques in the hope of reaching a reliable answer." In
Statistics of Deadly Quarrels Richardson presented data on virtually every war from 1815 to 1950, which he categorized using a
base 10 logarithmic scale based on the number of battle deaths a conflict produced. In this way, he was the first to observe that the sizes of wars appeared to follow a highly right-skewed
Pareto distribution, in which while small conflicts are relatively common, the very largest conflicts are orders of magnitude larger than the "typical" conflict. While conflicts' sizes can be predicted ahead of time, Richardson showed that the number of international wars per year follows a
Poisson distribution. On a smaller scale he showed a similar pattern for gang murders in Chicago and Shanghai, and hypothesized that a universal rule connected the frequency and the size of all "deadly quarrels". In the early 21st century, Richardson's work on conflict enjoyed a revival among conflict scholars, as his power-law distribution pattern was found in the statistics of several other kinds of conflict, including terrorism and violent mobs, and his work has informed the debate over the durability of the "
Long Peace" since 1946. Modern statisticians have shown that while Richardson's analyses were not rigorous by modern standards, his statistical conclusions largely hold up: the sizes and frequencies of armed conflicts plausibly follow a power-law pattern, and the rate of new wars is well-modeled by a Poisson distribution. ==Research on the length of coastlines and borders== Richardson searched for a relation between the probability of two countries going to war and the length of their common border. While collecting data, he found that there was considerable variation in the various published lengths of international borders. For example, that between Spain and Portugal was variously quoted as 987 or 1,214 km, and that between the Netherlands and Belgium as 380 or 449 km. The reason for these inconsistencies is the "
coastline paradox". Suppose the coast of Britain is measured using a 200–km ruler, specifying that both ends of the ruler must touch the coast. Now cut the ruler in half and repeat the measurement, then repeat: The smaller the ruler, the longer the resulting coastline. It might be supposed that these values would converge to a number representing the coastline's true length, but Richardson demonstrated that this is not so: the measured length of coastlines, and other natural features, increases without limit as the unit of measurement is made smaller. This is known as the
Richardson effect. At the time, the scientific community ignored Richardson's research. Today it is considered an element of the beginning of the modern study of
fractals.
Benoît Mandelbrot quotes Richardson's research in his 1967 paper
How Long Is the Coast of Britain? Richardson identified a value (between 1 and 2) that describes the changes (with increasing measurement detail) in observed complexity for a particular coastline; this value served as a model for the concept of
fractal dimension. ==Patents for detection of icebergs==