Consumer Price Index (CPI)

The consumer price index (CPI) measures the average change in prices paid by urban consumers for a basket of goods and services over time. Published monthly by the Bureau of Labor Statistics, CPI is the most widely followed inflation indicator. It includes categories like housing, food, energy, transportation, and medical care. The headline CPI includes all items, while core CPI excludes food and energy for a less volatile reading. CPI day is one of the most important dates on the options trader's calendar.

Why It Matters

CPI releases regularly produce 1-2% moves in the S&P 500 within hours — sometimes within minutes. For options traders, this makes CPI day both an opportunity and a risk event. Implied volatility builds into CPI releases and collapses afterward, creating tradeable IV crush opportunities. If you hold short-term options through a CPI print, you are making a bet on the number whether you intend to or not.

The market reacts not to the absolute CPI number but to how it compares to the consensus forecast. A CPI print of 3.0% when 3.2% was expected is bullish (less inflation than feared). A print of 3.4% when 3.2% was expected is bearish (more inflation than feared). The surprise relative to expectations drives the move.

How It Works

What gets reported:

• Headline CPI (Month-over-Month): The monthly change in prices. Even small differences (0.1% vs. 0.2%) move markets.
• Headline CPI (Year-over-Year): The annual inflation rate. This is what media headlines reference.
• Core CPI (Month-over-Month and Year-over-Year): Excludes food and energy. The Fed pays more attention to core readings.
• Subcategories: Shelter, used cars, medical services, airfares — specific categories can drive the overall number and provide forward-looking clues.

Market reaction dynamics:

• CPI below expectations: Stocks rally, especially growth/tech. Bond yields fall. Implied volatility drops (IV crush).
• CPI above expectations: Stocks sell off, especially rate-sensitive sectors. Bond yields rise. IV may stay elevated if the surprise is large.
• CPI in line with expectations: Muted reaction. IV crush still occurs because the uncertainty is removed.

How to trade around CPI:

• Selling premium before the report: Sell iron condors or strangles with short strikes beyond the expected move. Collect inflated premium. If the move stays within your range, IV crush works in your favor.
• Buying directional options: If you have a thesis on whether CPI will surprise hot or cool, buy calls or puts. This is a directional bet with binary-event risk.
• Avoiding the report: If you have open positions, be aware that CPI day can gap your stock and blow through your strikes. Close or hedge before the report if needed.
• Playing the aftermath: Wait for the dust to settle after the CPI reaction. The initial move sometimes reverses by end of day. Entering after the report removes event risk.

Quick Example

CPI is released at 8:30 AM ET and comes in at 3.1% versus the 3.3% consensus estimate. SPY gaps up 1.2% at the open. You had sold a 0DTE iron condor on SPY the previous day with wide strikes. The move stays within your range, and IV crushes from 18% to 12%. You buy back the iron condor at 10 AM for 55% of the premium collected. The CPI surprise helped your direction, and the IV crush amplified your profit.