My own experiences disagree. I have friends who started out in middle-class families and sunk lower. I also have friends who started out middle-class and rose

My own experiences disagree. I have friends who started out in middle-class families and sunk lower. I also have friends who started out middle-class and rose. IMHO, the biggest factors seem to be raw intellingence, willingness to move & chase money, and some 'luck' factors. But I can't imagine a world where nobody could change fortunes given reasonably common circumstances.