The primary limitation of both statistical poverty lines and market baskets of goods and services is that they cannot cover all the exceptions to the rule. Poverty lines work best when they are used to measure the incomes of large groups of people. They work worst when people try to apply them to individuals. Take the cost of housing, for example. Some people have mortgages and others do not.
Some people live in government-subsidized housing.
Some people live in well-insulated apartments where the rent includes heating, while others rent houses which are poorly insulated and have to pay sizable heating bills on their own. A couple with two young children might be able to manage with two bedrooms, but a couple with a teenage boy and a teenage girl would need three bedrooms. The people who draw poverty lines have to make compromises to keep the number of lines down to a reasonable total. The idea is to have poverty lines that cover the most common types of families in different parts of the country. All poverty lines are based on the number of people in the family, and some of them also take account of the size of the community where they live.