The Lombard Review

The inflation data with a missing month

Carry-forward prices bias CPI

A supermarket aisle in New Orleans
A supermarket aisle in New Orleans Photo: Infrogmation of New Orleans/Wikimedia Commons · CC BY-SA 4.0

Key dataNov CPI 2.7%

The Bureau of Labor Statistics released the November consumer price index showing headline inflation moderating to 2.7 per cent year-on-year. However, quantitative econometricians analyzing the underlying dataset uncovered an unprecedented statistical flaw: the entire monthly index was compiled with a missing month of price data.

Bowling Green, at the foot of Broadway in Lower Manhattan
Bowling Green, at the foot of Broadway in Lower Manhattan Photo: Epicgenius/Wikimedia Commons · CC BY-SA 4.0

The Carry-Forward Imputation Bias

Because federal field enumerators were legally prohibited from gathering retail price observations during the 43-day government shutdown in October, the BLS had no physical price data for that month. To bridge the gap, agency statisticians mechanically carried forward pre-shutdown price observations from September into October, dampening sequential price volatility. When November data was subsequently collected, the computational algorithm understated the true underlying price acceleration across durable goods and services.

The Lower Manhattan skyline from Liberty Island
The Lower Manhattan skyline from Liberty Island Photo: Percival Kestreltail/Wikimedia Commons · CC BY-SA 3.0

The Illusion of Disinflation

This technical carry-forward anomaly manufactured an artificial disinflationary trajectory. In reality, retail tariffs and supply-chain surcharges had been quietly implemented during the blackout period. November's 2.7 per cent inflation print is an econometric compromise compromised by missing data, offering the optical comfort of disinflation while concealing the unrecorded price increases that occurred during the federal shutdown.

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