Inflation definition and how it’s measured – latest CPI figure

The Consumer Price Index rose 2.9% year‑over‑year in August 2025, outpacing the 2.5% consensus and signaling higher price pressure for consumers and policymakers alike【1】.

What the CPI figure tells us

The 2.9% increase in the CPI‑U reflects a broader rise in the cost of living, exceeding both the forecast and the previous month’s 2.7% gain. Inflation is defined as a persistent rise in price levels that erodes the purchasing power of money【1】. When the CPI climbs faster than expected, it signals that consumer‑price pressures are building, prompting markets to price in tighter monetary policy. The 10‑year Treasury yield’s 5‑basis‑point rise mirrors investors’ anticipation of possible rate hikes to curb the overshoot.

How inflation is measured

Inflation is tracked primarily through two price indexes: the Consumer Price Index, which captures prices paid by households, and the Producer Price Index, which reflects wholesale prices paid by businesses【2】. Both indexes are constructed from a “basket” of goods and services—ranging from food and energy to housing and health care—whose monthly price changes are weighted to produce a single rate. The CPI figure for August 2025 represents the average price increase of this basket over the preceding 12 months, adjusted for seasonal effects【1】. In addition to CPI, the Producer Price Index (PPI) offers insight into upstream cost pressures that can later feed into consumer prices.

Why the rise matters for the broader economy

Mild inflation, typically around 2‑3%, is often viewed as a sign of a healthy, growing economy because it encourages spending and wage growth【2】. However, when inflation exceeds that range, it can erode real incomes and force central banks to tighten monetary policy, which in turn can slow growth and raise borrowing costs. The current 2.9% rate sits near the upper bound of the “Goldilocks” zone, raising the risk that policymakers may act more aggressively to prevent a wage‑price spiral—a feedback loop where higher wages and prices reinforce each other【1】.

What to watch

• Upcoming CPI releases: The next monthly CPI report (September 2025) will confirm whether the upward trend persists.
• Federal Reserve policy meetings: The Fed’s next FOMC meeting (scheduled for early November 2025) could adjust rates if inflation remains above target.
• Core CPI trends: Watch the core CPI (excluding food and energy) for underlying inflation pressure, as it often guides policy decisions.

The 2.9% CPI rise underscores that price pressures are intensifying, putting the onus on policymakers to balance growth with price stability. Whether inflation will settle back within the target range or trigger a tighter monetary stance remains the key question for markets.