One of my favorite websites, Dollar Street, imagines a world where everyone lives on the same street and the houses are ordered by income. The more time you spend on the website, the clearer it becomes that all of us have the same basic wants and needs. Take toothbrushing as an example. The families at the poorest end of the street use their fingers or sticks to clean their teeth. But once you reach a certain income level, everyone starts using a plastic toothbrush with bristles.