There are a small number of quite simple core concepts in marketing. Think of them as bricks. You use them to build a sales edifice so strong that, to paraphrase the Bard, it looks on tempests and is not shaken. Do it right and you will not merely survive the upheavals of business cycles. You will actually thrive in boom times and bust.
Here is one of the most important concepts. Nobody ever buys a quarter inch drill.