where 𝑛 𝑜,𝑗 and 𝑛 𝑒,𝑗 are the observed and expected number of infringements for zone j (Table ). The predicted number of infringements is given by 𝑛 𝑒,𝑗 = 𝑝 𝑁 𝑗 (2) 𝑁 𝑗 is the number of samples taken in zone j and p is the average probability of an infringement. When it comes to consider the 5-year period data is aggregated over 5 years and this data is processed in an identical way to that in a single year.