1.
The Classical Model builds on the principles developed in microeconomics to explain how equilibrium production and employment might be determined from profit maximizing and utility maximizing behavior.
From the system of dynamic model of the economy we can see that, as the production increased, the income will increase. And then both saving and consumption will increase. From this point, there are two ways to go. More consumption will decrease the production. But more saving will cause more investment and raise the technology, more investment will increase the capital, the increasing of capital will increase the production, in this way our economy will growth.
In a short way, after the increasing of income, if people put the majority of their income in the bank, instead of spend all of their money just for having fun, our economy will grow.

2. In the year 1931, some government and private experts were together to discussing our economy, but by that time they can’t give out enough data and reliable statistics. In 1934, they send out Simon Kuznets to figure out how to calculate the national accounts in a set of uniform. And that is how he came up with GDP. As the inventor of the GDP, Simon Kuznets had this to say in his very first report to the U.S. Congress in 1934, he said: “the welfare of a nation scarcely be inferred from a measure of national income.” In 1962, Kuznets stated: “Distinctions must be kept in mind between quantity and quality of growth, between costs and returns, and between the short and long run. Goals for more growth should specify more growth of what and for what.
We use GDP as a measurement of economy because All these items notwithstanding, GDP per capita is often used as an indicator of standard of living in an economy, the rationale being that all citizens benefit from their country's increased economic production. The