For almost two years the economy has been stumbling on a rocky path marked by soaring inflation, record-high interest rates and a constant specter of fuel shortages. During this period the Midwest, which includes the Seventh Federal Reserve District, has shouldered a disproportionate share of the trouble. Primarily, this reflects reduced demand for the products of some of the dominant industries in this region — cars and trucks, construction equipment, agricultural equipment, recreational vehicles and home appliances. Residential construction also has been much more seriously depressed here than nationally, partly because of slower growth of population.