Why do you think beligium is represented by a young girl?

Because this is the kind of image that Belgium wanted to convey. A young person as a representative of a country, which makes it a symbolism, as people treat young people as if they have no opinions and cannot argue, or are just a property of the parents. This girl brings a great analogy of the power of young people and how we should encourage them.

disequilibrium means that either supply is greater than the demand for an available good, or that the demand for a product outstrips the available supply. it implies that the price for a is either too low creating large demand, or too high creating a large surplus of supply.