I'm neither an economist or mathematician. But I'm smart enough to observe my surroundings. I observe that the middle class is shrinking rapidly. Wealth concent

I'm neither an economist or mathematician. But I'm smart enough to observe my surroundings. I observe that the middle class is shrinking rapidly. Wealth concentration is increasing rapidly. Income has not kept up with the price of goods. And it's increasingly difficult for working people to accumulate wealth. Can you point me to other theories which articulate the cause of my observations?