Lamarr and Anthiel received a patent in 1941, but the enormous significance of their invention was not realized until decades later. It was first implemented on naval ships during the Cuban Missile Crisis and subsequently emerged in numerous military applications.
Cash back credit card reward programs started out rather simply, offering a flat percentage rate (typically 1 percent of purchases) rebated back to the customer in the form of a check at the end of the year or a statement credit.
Credit card debt is often the best target to get fast results. Paying down credit card debt is typically rewarded more because you are paying down riskier (unsecured) debt and lowering your credit utilization. Pay a whole credit card off or at least get it under 10% and you will really see some impact.