How the BLS Builds the CPI
The CPI is not a rough estimate but a carefully built, survey-driven system refined over more than a century. To construct it, the BLS gathers price data on hundreds of everyday goods and services, known as the “market basket.” This effort spans roughly 8,000 housing units and 23,000 retailers, service providers, and online outlets across 75 urban areas nationwide, creating a detailed snapshot of how prices move in the real world.
Approximately two-thirds of that price collection is done by personal visits from CPI data collectors to brick-and-mortar stores. The remaining data are collected by telephone or on outlet websites and apps. This is painstaking, boots-on-the-ground work — and it takes time.
The basket of goods being tracked, and how much weight each category carries in the final number, is determined through a separate process. The BLS asks thousands of families to provide detailed expenditure data through the Consumer Expenditure Survey, with over 20,000 consumer units participating each quarter. To track frequently purchased items like food and personal care products, approximately another 12,000 consumer units keep detailed spending diaries over a two-week period.
All of that data gets compiled, checked, weighted, and published once a month. By the time you read the headline CPI number, the prices behind it were largely collected weeks earlier.
How Truflation Does It Differently from CPI
Truflation takes a fundamentally different approach. Rather than relying on in-person surveys, it pulls from a constant online stream of digital price data in real time. With access to more than 10 million data points, compared to the BLS’s roughly 80,000, it delivers daily updates and uses a flexible methodology that adapts quickly to shifting global market conditions.
The US index taps 30+ data sources and over 15 million prices of goods and services. Data providers include names like NielsenIQ, Amazon, Walmart, Zillow, Trulia, AAA Gas Prices, JD Powers, CarGurus, Numbeo, CoreLogic, Trivago, Hilton, and Hyatt, among many others.
Rather than a monthly snapshot, Truflation runs on a daily cycle. Data is collected, checked for quality, then processed to produce an updated index with a one-day lag.
Category weightings are reset yearly to reflect current consumer behavior, resulting in an inflation reading that captures prevailing market conditions rather than data collected several weeks earlier.
Truflation Leads CPI by About a Month
One of the more practically useful characteristics of Truflation is that it tends to signal where CPI is heading before the official number is released. In stable environments, this lead is roughly 40–45 days, reflecting the natural informational advantage of a real-time index relative to a monthly survey-based measure.
This lead is not incidental; it emerges from core methodological differences — specifically real-time digital price collection from online marketplaces, utilities, insurance datasets, and rental feeds, along with millions of daily observations and no smoothing or imputation, which allows Truflation to reflect actual market conditions immediately — in contrast to CPI, which applies multi-month smoothing and uses imputed data in several categories.
One of Truflation’s most practical advantages is its ability to signal where CPI is headed before the official release. In stable conditions, this lead is typically about 40 to 45 days, reflecting the natural edge of a real-time index over a monthly, survey-based measure.
This lead is not accidental. It comes from fundamental differences in methodology, including real-time digital price collection across online marketplaces, utilities, insurance data, and rental feeds, combined with millions of daily observations and no smoothing or data interpolation. As a result, Truflation captures market conditions as they evolve, while CPI relies on multi-month smoothing and estimated data in several categories.
In plain English: When looking at Truflation vs. BLS CPI, with Truflation, we see price changes in real time. Although the BLS eventually captures those same changes, it’s only after they’ve been collected, processed, and averaged into a monthly release, usually several weeks later.
So, Why Is Truflation Sometimes Lower Than CPI?
Here’s the part that catches many people off guard. A common criticism of the CPI is that it understates true inflation, yet Truflation, built to be more responsive and comprehensive, often comes in below the official CPI reading.
The biggest reason is how each index handles housing costs. The single weightiest item in the CPI, at about 22.3%, is “owner’s equivalent rent of primary residence” — essentially how much homeowners would have to pay if they were renting their homes. This is an imputed (estimated) figure, not an actual market transaction — and it tends to lag actual rent movements significantly because it’s based on a rolling survey of existing leases rather than new ones.
The major reason for the difference is how each index handles housing costs. The CPI’s largest component (about 22.3%) is “owner’s equivalent rent,” an estimate of what homeowners would pay to rent their own homes. It is not based on actual transactions and tends to lag real market rents because it relies on surveys of existing leases rather than current listings or new agreements.
Truflation pulls live rent data from sources like Zillow and Trulia, which reflect current asking prices. When rental markets are cooling, Truflation will show that decline much faster than the BLS. During the post-pandemic disinflation of 2023 and beyond, this housing methodology gap meant Truflation was showing falling shelter costs well before the CPI caught up.
In other words, Truflation isn’t necessarily “more accurate” or “less accurate” than CPI in a simple sense — it measures some things differently, particularly shelter, and those differences can push the reading in either direction depending on market conditions.
Truflation vs BLS CPI, Not Just Two Numbers
Neither index is perfect, and neither tells the complete story on its own. Truflation has the advantage of speed, breadth, and real-time responsiveness. But the BLS’s CPI is followed more broadly and thus has the ability to move markets.
It’s worth noting that despite their methodological differences, the two indices track each other remarkably closely. Danielle DiMartino Booth — former Federal Reserve insider and CEO of QI Research — is one of Truflation’s most prominent advocates. She has noted that since the Federal Reserve began its tightening cycle, the correlation between headline CPI and Truflation has tightened from .97 to .99, adding: “You follow Truflation every day, listen to me!” That’s about as close as two independently constructed indexes can get.
It’s worth noting that despite their methodological differences, the two indices move remarkably in sync. Danielle DiMartino Booth, former Federal Reserve insider and CEO of QI Research, is one of Truflation’s most vocal advocates. She points out that since the Fed began its tightening cycle, the correlation between headline CPI and Truflation has risen from 0.97 to 0.99.
For investors and financial analysts, Truflation functions best as an early warning system — a look at where inflation is likely heading before the official data confirms it. For long-term economic research and historical comparison, the BLS CPI remains the standard.
The Hidden Secret of Truflation
One “problem” with Truflation is that in order to get the actual current Truflation numbers, you have to be a subscriber. The free numbers that they post on the site are actually delayed numbers. So the numbers you see on the site are not current, and when inflation moves quickly, like they did recently with the War in Iran, if you think the old numbers are actually the current numbers, it could be misleading. On April 8th, Truflation released their March Inflation report as a Free report.
It said, “The dominant story this month is oil, oil, and more oil. The price of WTI crude surged from $71.99 at the start of the month to $101.38 by the end of March, marking the first time since 2022 that prices have breached the $100 per barrel threshold. This sharp move has flowed directly into gasoline prices, which surpassed $4.00 per gallon nationally on March 30, up from $3.06 at the beginning of the month, according to the Truflation U.S. CPI Gas Index… What does this imply for Truflation’s forecast of the BLS CPI headline inflation for March? Truflation is projected at 3.3% year on year, slightly below the market consensus of 3.4%, which itself spans a relatively wide forecast range of 3.0% to 3.8%.”
So, Truflation is no longer saying that Inflation is 1.78%; it is actually IDENTICAL to the March BLS CPI number.
Understanding how each index is built goes a long way toward understanding why they sometimes diverge. The data isn’t wrong — it’s just measuring the same economic reality through very different lenses, on very different timelines.
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