## How to Use Tom's Inflation Calculator

Five selectable data sets let you fine-tune Tom's Inflation Calculator for your own purposes. The default data is U.S. Price Inflation (CPI-U, Annual Average), 1666 to 2070. Click the Options button to choose a different data set. All of them let you perform calculations forward or backward in time, for any years within their ranges.

For most purposes, the default data is sufficient. It's the U.S. government's Consumer Price Index for All Urban Consumers (CPI-U), Annual Average. Special-purpose data sets include the CPI-U from December to December instead of Annual Average; the Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W); U.S. Medical Cost Inflation; and U.S. Price Inflation (ShadowStats). For information about these specialized data sets, scroll down this page to the section "Changing Data and Formatting Options."

See more instructions and examples below. For a question-and-answer format of basically the same information, see Tom's Inflation Calculator Frequently Asked Questions.

## Two Examples Using the Calculator

Example #1 (CPI-U inflation, backward in time): Suppose you just paid \$3.00 for a gallon of regular gasoline. Somebody tells you that gasoline cost only 50 cents a gallon in 1975. But was gasoline really cheaper back then, after allowing for inflation?

• To find out, make sure the default data set is selected: U.S. Price Inflation (CPI-U, Annual Average). The current data set is indicated below the row of Inflation Calculator buttons. You can change it by clicking the Options button. By default, the Inflation Calculator automatically starts with U.S. Price Inflation (CPI-U, Annual Average).

• Enter 3.00 in the Dollar Amount field.

• Enter 2011 (the default) in the Starting Year field.

• Enter 1975 in the Target Year field.

• Click on the Calculate button.

The answer -- in this case, \$0.67 -- appears in the Converted Amount field. So, after adjusting for inflation, a gallon of gasoline is more expensive today (67 cents) than it was in 1975 (50 cents).

Example #2 (CPI-U inflation, forward in time): Let's say you were making \$25,000 a year in 2000. Have your wages kept pace with price inflation over the last ten years?

• To find out, start with the default data set again: U.S. Price Inflation (CPI-U, Annual Average).

• Enter 25,000 in the Dollar Amount field.

• Enter 2000 in the Starting Year field.

• Enter 2011 (the default) in the Target Year field.

• Click the Calculate button.

The answer -- in this case, \$32,684.15 -- appears in the Converted Amount field. If your current salary is less than that amount, you haven't kept up with general inflation. Time for a raise!

If you are a clerical or hourly-wage worker, try repeating this calculation using the CPI-W inflation data. The CPI-W tracks inflation for that subset of U.S. workers. Click the Options button to choose the CPI-W data set. Then click OK and click the Calculate button again. The new answer should be \$32,775.41.

## Changing Data and Formatting Options

You can change data sets or switch dollar formatting on or off after clicking the Options button. This opens the Inflation Calc Options window. The default data set is U.S. Price Inflation (CPI-U, Annual Average) from 1666 to 2070.

In the Inflation Calc Options window, you can select from five data sets:

• U.S. Price Inflation (CPI-U, Annual Average), 1666 to 2070
• U.S. Price Inflation (CPI-W), 1914 to 2010
• U.S. Medical Cost Inflation, 1936 to 2010
• U.S. Price Inflation (CPI-U, December to December), 1914 to 2010
• U.S. Price Inflation (ShadowStats), 1970 to 2010.

Note that with any data set, you can convert amounts for one year past the last year of available data: 2071 for CPI-U inflation, and 2011 for CPI-W inflation, medical-cost inflation, December-to-December inflation, and ShadowStats inflation.

The Inflation Calc Options window also lets you turn dollar-and-cents formatting on or off. The default setting is on.

• U.S. Price Inflation (CPI-U, Annual Average): This measure of inflation is often quoted in news stories and is the basis for cost-of-living adjustments (COLAs) by Social Security and many union contracts. It's the Consumer Price Index (CPI) for All Urban Consumers (CPI-U). It represents the annual average of monthly inflation rates in a calendar year for goods and services purchased by about 87 percent of the U.S. population. This is the default data set in Tom's Inflation Calculator.

• U.S. Price Inflation (CPI-W): This data set is the Consumer Price Index (CPI) for Urban Wage Earners and Clerical Workers (CPI-W). It's a subset of the CPI-U that includes clerical and hourly-wage workers, or about 37 percent of the U.S. population. If you are such a worker, this data is supposed to reflect your purchases more closely. Also, note that one proposal for reforming Social Security is to tie the annual COLAs to CPI-W inflation for lower-income recipients, and tie the COLAs to CPI-U inflation for higher-income recipients. My Inflation Calculator lets you compare these two inflation rates.

• U.S. Medical Cost Inflation: This data set covers U.S. medical-cost inflation since 1936. It's actually part of the overall CPI-U. (My thanks to Sam Baker for suggesting this breakout.) To use this data set, click the Options button and choose it in the Inflation Calc Options window. Please note that this data set tracks the inflation of actual medical costs, not the inflation of health-insurance premiums, which rise faster than medical costs.

• U.S. Price Inflation (CPI-U, December to December): New since version 7.1 is a data set for calculating U.S. price inflation using the government's December-to-December data instead of the annual average data. The difference is subtle. The December-to-December data compares retail prices in December of a given year with retail prices exactly one year earlier. The annual average data is the mean average of inflation rates for all 12 months in a calendar year.

Over time, the difference between these two inflation rates rarely matters. However, my Inflation Calculator now includes the December-to-December data because some news stories refer to it, and occasionally, people ask why the inflation rates in my program seem to vary from those they heard about elsewhere. For example, in 2009, the annual average inflation rate was -0.4% (actually, deflation), whereas the December-to-December inflation rate was +2.7%.

The annual average rate is used more widely, so my program defaults to it. The December-to-December data is available by clicking the Options button and selecting the data set in the Inflation Calc Options window. Note that this data covers only the years 1914 to present, unlike the annual average data, which covers the years 1666 to 2070.

• U.S. Price Inflation, ShadowStats: New since version 7.2 is a data set for calculating U.S. retail price inflation using statistics not compiled by the U.S. government. Instead, this data set is provided with the permission of ShadowStats, a private organization. (My thanks to ShadowStats author John Williams for his cooperation.)

ShadowStats data is an alternative to the official inflation data from the U.S. Bureau of Labor Statistics. ShadowStats claims to make a more accurate estimate of inflation. In general, ShadowStats says that actual inflation is much higher than the government's official statistics. I cannot vouch for the accuracy of ShadowStats data, just as I cannot vouch for the accuracy of U.S. government data. ShadowStats data is proprietary and copyrighted. Although ShadowStats has kindly granted me permission to use some of its data in my Inflation Calculator, my program is not permitted to display the data. For information about ShadowStats, see www.shadowstats.com.

Far-future forecasts: New since version 5.0.2 are inflation estimates extending as far forward as the year 2070, as part of the U.S. Price Inflation (CPI-U, Annual Average) data set. These inflation rates are based on forecasts by the Congressional Budget Office (for the years 2011-2020) and my own guesstimates for years beyond the CBO forecasts. (I'm guessing 3.0 percent per year.) These inflation estimates allow you to roughly estimate how much your retirement savings will be worth in future years. (My thanks to Penelope Reznor and Kodi Wolf for suggesting these extensions.)

## Displaying Inflation Rates

You can see inflation rate percentages for the range of years you've entered in the year fields by clicking the Show Rates button. If the inflation percentage is a negative number, it indicates deflation for that year. You can also view inflation rates without performing an inflation calculation. Simply enter any range of years in the year fields and click the Show Rates button. If you select a range of years beyond the available data, the program displays the most data available.

New since version 7.0.7: the window that appears after clicking the Show Rates button also displays the cumulative inflation rate for the range of years selected. Note that the cumulative rate is derived iteratively, not merely by summing the inflation percentages for each year. The cumulative number shows the total amount of inflation during the years selected. (Thanks to Cy Coleman for suggesting this feature.)

ShadowStats alternative inflation data is proprietary and cannot be displayed by my program.

## A Few More Hints

If you enter a very large number to convert, the result may not fit in the answer field and the program will say "ANSWER TOO LARGE." But you can still obtain an answer by switching off the "Format Raw Answers As Dollars And Cents" checkbox in the options window. The raw answer will be in scientific notation. You can also switch off this option to see if the raw answer includes fractions of pennies. The program truncates raw answers instead of rounding.

Note: This program assumes the target year isn't finished yet, so it doesn't include the target year's inflation rate in the calculation. For instance, if you calculate inflation from 1990 to 2010, the program uses inflation rates from 1990 through 2009 to compute the answer. To include the target year's inflation rate in the calculation, choose a target year one year past your target -- e.g., 2011 for 2010.

In other words, the program has a worst-case error of 12 months and an average error of 6 months. In the worst case, it will understate the actual amount of inflation by 12 months if the target date of your target year is December 31. If the program were written to include the target year's inflation rate in the calculation, the worst-case error would still be 12 months, except it would tend to overstate the actual amount of inflation if the target date of your target year were January 1. I've chosen the first method because you're more likely to be seeking an inflation-corrected amount for sometime during the target year, not for the last day of the year. (However, note that if you display the annual inflation rates by clicking the Show Rates button, the target year's rate will appear in the window, even though it's not included in the calculation.)

## Data Sources

This program uses inflation data from several sources, including Global Financial Data, Economic History Services, the U.S. Bureau of Labor Statistics, the Congressional Budget Office, and ShadowStats.

The most widely quoted inflation rate is the U.S. government's Consumer Price Index (CPI), 1914 to present, as compiled by the U.S. Bureau of Labor Statistics. By default, my Inflation Calculator uses the CPI-U (CPI All Urban Consumers) data, not seasonally adjusted (data series CUUR0000SA0). Data before 1914 was mostly reconstructed by economists from old records and is less reliable. The CPI-W data is also from the U.S. Bureau of Labor Statistics, 1914 to present (data series CWUR0000SA0). The medical-cost data is a subset of the government's CPI but has been tracked only since 1936 (data series CUUR0000SAM). The December-to-December inflation is also from the U.S. Bureau of Labor Statistics and extends from 1914 to present (data series CUUR0000SA0). The ShadowStats price-inflation data is from a private organization, not the U.S. government.

Inflation rates for 2011 through 2020 are the latest forecasts from the Congressional Budget Office, a nonpartisan source. Inflation rates for years beyond 2020 are my own guesstimates, based on an average rate of 3.0 percent per year.

If you want to learn more about how the U.S. Bureau of Labor Statistics gathers inflation data, the San Francisco Chronicle published an interesting article about a BLS "shopper." These professional shoppers spend their days canvassing stores, checking retail prices on the kinds of products American consumers are buying. The article was published on April 30, 2006, and is headlined, "A Measure of What's in Store". On February 24, 2008, the San Francisco Chronicle published an article discussing the shortcomings of the CPI: "Consumer Price Index a Real Guessing Game".

Some people believe the U.S. government deliberately distorts its inflation data for devious reasons. For instance, some Social Security retirees believe they are cheated out of larger cost-of-living adjustments because the government understates the actual CPI, which is the basis for adjusting Social Security benefits. Other people assert that the government overstates the CPI. People who occasionally write to me on this subject never provide data to support their claims. However, for a contrarian view of U.S. inflation statistics, see ShadowStats.com, which has granted me permission to use its alternative inflation statistics as an alternative data set in my Inflation Calculator.

## Other Calculators

The U.S. Bureau of Labor Statistics has an inflation calculator. It uses the same CPI-U (annual average) data that my Inflation Calculator uses by default. However, answers may vary when converting values to the present year, because the BLS calculator includes the latest monthly inflation data. For my calculator, I update the data only once a year (in January), when the data is more settled. (The government often revises its monthly inflation data and makes seasonal adjustments.) When converting between other years, rounding errors during calculations may cause insignificant differences between the answers. Also, the BLS calculator covers only the years 1913 to present. Unlike my Inflation Calculator, it doesn't include historical data going back to 1666 or the forecasts to 2070. Nor does it have alternative data sets.

For an interesting Italian inflation calculator with lots of features, see www.rivaluta.it

Penn State University has a Living Wage Calculator that accounts for differences in cost of living in various parts of the U.S. It's part of Penn State's Poverty in America Project.