Tracking Bitcoin's Purchasing Power vs. Inflation
May’s data is in, and once again the Bitcoiner Price Index (BPI)—our gauge of consumer-price changes denominated in BTC—shows a steep deflationary trend compared to traditional CPI inflation.
Snapshot of the Latest Data
For the most recent month ending April 2025:
CPI YoY Change: +2.38%
BPI YoY Change: –35.54%
The current Bitcoin price stands at $109,628.61², with Bitcoin posting a 5.29% gain over the past month, a 62.85% increase over the past year, and a 193.60% rise over the past four years.
(Red indicates CPI > 2%)
What Does This Mean?
CPI vs. BPI
The Consumer Price Index (CPI) measures how much a standard basket of goods costs in fiat dollars—right now, prices are rising at about 2–3% per year. The Bitcoiner Price Index (BPI), which divides that same CPI by Bitcoin’s price, is plunging: a –35.54% YoY BPI tells us it takes over 35% fewer BTC today to buy the same goods than it did a year ago. For Bitcoiners, that deflationary signal is as bullish as it gets—your purchasing power in BTC continues to accelerate.
Averages and Trendlines
Beyond the latest month, the long-run picture remains striking:
Averages of YoY Changes
CPI: +3.26%
BPI: –17.42%
On average, while fiat consumer prices creep up ~3% per year, goods priced in BTC fall nearly 18% per year.
Trendline Slopes (monthly YoY change)
CPI: +0.0296 percentage points per month
BPI: +0.4363 percentage points per month
Both slopes are positive—but remember, the BPI series itself remains deeply negative. A rising slope here simply means the rate of deflation in BTC terms is easing slightly—but it’s still deflation.
Compound Annual Growth Rate (CAGR):
Let’s take a moment to explain CAGR, as it’s a key metric in this updated analysis:
CAGR represents the smoothed, annualized rate of growth of an index over a period of time. Imagine if the CPI or BPI had grown at a steady rate each year; the CAGR tells you what that steady rate would be.
The formula is:
CAGR = (Ending Value/Beginning Value)^(1/n) − 1
For our analysis:
CPI CAGR: +3.06% per year (typical inflation)
BPI CAGR: –44.15% per year
A BPI CAGR of –44.15% means that, if the BPI had fallen at a steady annual rate, it would have declined by 44.15% each year—demonstrating Bitcoin’s enormous compounded gains in purchasing power against consumer prices.
Implications for Bitcoiners
For those who believe in a Bitcoin standard, these numbers carry powerful implications:
Real-World Buying Power
A sharply negative BPI CAGR shows Bitcoin doesn’t just preserve value—it multiplies purchasing power over time.
Inflation Hedge
While fiat loses ~3% purchasing power annually, Bitcoin delivers an equivalent of 40+% annual “deflation” in goods prices for its users.
Market Stabilization
The slight slowdown in the BPI trendline slope (0.4363 vs. last month’s 0.4614) hints at a maturing market. Even so, the deflationary trend remains overwhelming.
Conclusion
May’s update reaffirms the Bitcoin-standard thesis: fiat currencies wobble under steady inflation, but Bitcoin continues to drive dramatic deflation in BTC terms. As we head into June, keep an eye on whether this powerful trend endures—or whether the next chapter of Bitcoin’s purchasing-power story begins.
Stay tuned as we continue to refine this analysis and track the trends that matter most to the #Bitcoin community. Feedback and suggestions welcome!