CPI Decoded: Measuring the Purchasing Power of the Dollar

Understanding the Consumer Price Index and the role it plays in determining the Fed’s market decision will go a long way toward improving your forecasting abilities. The modern Consumer Price Index (CPI) was first published in 1913 by the U.S. Bureau of Labor Statistics (BLS), the same year the Federal Reserve was established. While earlier retail price indexes date back to 1884, the CPI as a national inflation benchmark began in the early 20th century. Today, it still plays a vital role. Here’s what you need to know.

Consumer Price Index

The CPI was originally published by the U.S. Bureau of Labor Statistics (BLS) in 1884 as a way for economists to track retail food prices. At the time, this tracking was crucial to monitor the effects of tariffs. By 1913, the practice had become standard. It would continue to help economists monitor markets until 1919.

At this time, the CPI was broken into 32 city-specific indexes. These included many of the categories that you recognize today, such as food, clothing, and rent. In 1921, the entire index was merged to create a national CPI.

This method of tracking national costs was upgraded in WWII. It was then that weighted averages and some wartime exclusions were integrated. In 1953, the CPI-U standard was applied. This transformed the measurements into one standardized rate that covered 93% of the US population.

Track Price Changes

Today, the CPI remains one of the best ways for the Fed and investors to track price changes across a myriad of goods. This helpful tool examines the prices paid by consumers for essential items and compares them to previous years to ascertain inflationary effects.

Source – BLS

The CPI includes 8 major categories. These categories are weighted. They cover:

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How to Use It:

There are several ways you can use the CPI to improve your investment strategy. For one, you can use it to monitor inflation. Understanding inflation and the Fed’s next move can help you to position for potential market changes.

The Fed relies on this metric to make key inflationary adjustments. Some businesses also leverage this metric to determine their wages, alongside the social security department, which uses the metric to determine payouts. Here is the equation used by the Fed to determine CPI:

CPI = (Cost of fixed basket today / Cost in base year) × 100

Inflation Rate = [(New CPI – Prior CPI) / Prior CPI] × 100

Unions are another group that relies on the CPI to ensure their members receive fair wages when compared to the cost of living. When combining these scenarios with investors using the tool to determine future demand, it’s easy to see why CPI is important to many investors’ strategies.

Headline CPI:

There are several ways to examine the CPI, with the main way being to review the headline CPI. This form of CPI includes all the categories mentioned. It offers a broad consensus on the market and inflation, measuring the effects across key sectors. As such, it’s ideal for capturing the true scope of price changes experienced by consumers.

Core CPI:

The Core CPI differs from the headline option in that it removes Food and Energy prices. This approach is meant to eliminate some of the most volatile items from the report. This approach is ideal for plotting policies as it helps to reveal underlying inflation based on monetary actions and not supply shocks.

Notably, the Core CPI is less volatile due to these changes. Additionally, the weighted average is changed slightly, with housing accounting for 40% versus only 33% in the headline CPI data. This strategy improves the Fed’s ability to eliminate short-term noise.

Supercore CPI

The Supercore CPI emerged following the pandemic as a way to isolate the unique financial pressures caused by lockdowns—specifically, the volatile shifts in wages and service-side demand. By removing housing costs from the Core CPI, this metric allows the Fed to focus strictly on the services sector.

The goal is to enable the Fed to notice key changes in labor-driven inflation and provide an early warning of any potential “wage-price spirals,” where rising labor costs lead to higher service prices, which in turn drive further wage demands.

The 2% Target:

Currently, the Fed has set a goal for 2% inflation. This setting means that as long as the inflation sits above 2%, the group will leverage inflation to help cool the economy and reduce consumer demand and prices.

The decision to go with 2% over zero makes sense, as anything less than 2% will entice investors to take on major debt burdens. The Federal Reserve formally adopted a 2% inflation target in January 2012 under Chairman Ben Bernanke. This target was chosen as a balance between price stability and economic flexibility, providing a buffer against deflation while preserving purchasing power over time.

Dot Plot

The CPI plays a vital role in the Fed’s quarterly dot plot releases. These charts show a non-binding consensus on the Fed members’ particular perspective towards altering interest rates. Consequently, tightly grouped dots signal consensus, while loose grouping means the group is split.

The Market Reaction:

Notably, any changes to the CPI will result in market reactions. For example, if the CPI exceeds expectations, it can result in the Fed raising rates. This maneuver effectively slows borrowing by raising the cost of accessing funds. This move is meant to lower spending and tighten capacity, dropping CPI to the goal 2%.

Lower than Expected CPI:

Conversely, if the CPI is lower than expected, it’s seen as a positive sign for stock investors. For one, it hints that the Fed is likely to cut interest rates in the near term. It also means that inflation is cooling, opening the door for more investor participation, as seen in past NASDAQ momentum.

CPI Decoded: Measuring the Purchasing Power of the Dollar

Understanding why and how the national CPI affects the market enables you to plan better. Thankfully, this helpful data gets issued monthly, allowing you to stay up to date and in line with the Fed’s perspective. Consequently, the CPI should become a crucial component of your investment strategy planning moving forward.

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