In this lesson, Nick Palazzolo, CPA, demystifies the Consumer Price Index (CPI), showcasing it as a vital indicator of inflation through a detailed exploration of its underlying calculations. With his usual flair for making complex concepts accessible, Nick delves into the percent change formula, illustrating its applicability to everyday scenarios like stock price movements and changes in grocery costs. By comparing historical and current CPI values, he clarifies how inflation rates are determined, stressing the significance of understanding these changes over set periods. Furthermore, Nick expands on how the CPI relates to household expenditures, emphasizing its impact on personal finances. He also introduces the Producer Price Index (PPI), drawing parallels and distinguishing its focus on the costs borne by producers. Through practical examples, Nick ensures that the quintessential percent change formula is not just a theoretical concept but a practical tool for interpreting economic trends and personal financial analysis.