Economy can the political direction, guidance, and direction to the city can be a measure of country's economy. Because they both have a relationship and engage in mutual support.
Political economy can right direction and it is a measure of the political economy of the country because the two things are related and engage in mutual support.
The economy can lead the direction of politics and political direction, it can measure the economy of the country, because both of these have the relationship and participate in support to each other.