How do countries and individuals become rich? Human history provides a clue. One of our most defining moments as a species took place some 10,000 years ago, when a group of humans started to switch from hunting and gathering food to growing it. This allowed them to settle down (in an area called Mesopotamia). If they produced more than they consumed, they could save for the future. With proper storage facilities, they no longer needed to eat and drink everything they had; instead they could put some aside literally for "rainy days", and, even more importantly, invest some of the agricultural output to produce even more.
Now zoom forward several thousand years: saving has become central to individual and collective prosperity. As a rule of thumb those who save more become wealthier because foregoing consumption today allows one to invest in the future (e.g. you can save to buy a bicycle, a car, or a house). Businesses can invest in new equipment and governments in new roads, schools and health facilities. All of these investments are associated with better economic futures.
People and companies tend to save and invest if they can trust the institutions that manage their money and the economy at large. In the past, it was not always safe to keep deposits at banks in many African countries. It is different today. In fact some may feel more secure entrusting their savings to African banks than those in Europe (as depositors in Cyprus’ banks recently realized). But you need more than robust and credible banks for increasing savings and investments. Investors will only enter and stay in large numbers if they can trust that the state won’t change the rules of the game in mid-course.