The IPAT model is a model that is designed to base environmental impact, the “I” in the model, in relation to Population, Affluence, and Technology. Therefore, the greater numbers in those columns, the greater the impact on the environment will be. As such, the equation is formulated like this: Impact equals Population multiplied by Affluence multiplied by Population. Population, as defined by the equation, is the number of people in a place, and the more people there are, the greater the strain on the environment, as each person takes up more space in the environment, uses up natural resources, as well as generating waste from those actions, further impacting the environment. For affluence, the higher the number means that the place has a greater per capita wealth, which works in conjunction with resource consumption as an illustrator of how much is consumed by a population over a period of time. The final factor, technology, can be the most impactful factor of all, as humans have found ways to utilize technology that not only very, very effectively increases impact on the environment, but severely outweighs the environmental impact of the number of people that are in that place, becoming possibly the most impactful factor. There is another factor, Sensitivity, that is not officially a part of the IPAT model, but takes into account the environmental “carrying capacity”, or the ability for the place to take the population, affluence, and technology not only successfully but sustainably, greatly altering whether or not the place can actually take the factors being forced upon it. 

The case given is a difference between two towns that have different environmental impacts on the land. Town 1 has a population of 100 people, and has an average income of 50,000 dollars. Town 2 has 500 residents and an average income of 25,000 dollars. At face value, town 2 already has a greater impact, given that when calculated through the IPAT model, town 2 has a greater value than town 1. But the last value, technology, is not easily calculated from the information of the towns, as it only provides that town 1 uses efficient heating and town 2 uses inefficient heating, but still points to town 2 having a greater environmental impact. The IPAT model is useful when calculating these numbers, but can run into some issues when the technology aspect of it is not so easily calculated as there is no figure that can be plugged into technology, only ideas of efficiency and inefficiency. However, if one found values for those, then the IPAT model would work quite well, and is generally a pretty good judge in practical usage.