After the 1970s, what did economists learn? Responses In the long-run, an economy can be affected by changes in aggregate supply. In the long-run, an economy can be affected by changes in aggregate supply. Changes in the economy in the short-run are best understood by looking at both aggregate demand and aggregate supply. Changes in the economy in the short-run are best understood by looking at both aggregate demand and aggregate supply. In the long-run, an economy can be affected by changes in aggregate demand