Natural Economics
To find natural rates for a process, you remove all arbitrary and synthetic (all artificial, man-made) interference with the process, and then you record the results.
If you hold a rock in your hand, the rock is motionless--but if you let it go, the natural accelerator (gravity) causes it to fall at a precise rate of acceleration estimated by scientists as 9.8 meters per second per second.
The natural rate of acceleration holds true, or more precisely, is contextually-true and almost entirely sufficient, for objects close to Earth. Exceptions to the rule, such as feathers falling slower than bowling balls, are fully explainable and actually help to prove the rule.
Economists who attempt to define what is natural by only looking at what is artificial--by looking at "average" rates under heavy artificial interference with economy activity--are like physicists attempting to measure the rate of free fall by studying the free fall of a motionless rock being artificially propped up or held in someone's hand.
This is wrong-headed. To find the natural rate of free fall while studying a rock, you have to let it go (eg, laissez-faire).
In other words, the place to look for natural rates is not the average of recent decades (which come with at least a 7-fold increase in economic intervention as compared to laissez-faire), the best estimates of natural rates are, actually, the "best estimates" which are to be found in the recorded history of economic outcomes.
Again, like the analogy of the falling rock, you do not find natural rates by studying unnatural processes (processes which have been artificially interfered with).
Instead, you study processes when they are under the least interference. From 1946 going forward--when the Employment Act authorized federal government interference into the US economy--there has been an annual average increase in economic interference in the US.
Prior to 1946, interference levels undulated (went up and down) but at a low absolute (overall) level. After 1946, interference levels began to go "up and up"--and not "up and down" anymore (when "up and down" are measured relative to the absolute level of interference to begin with).
In other words, to find the natural rate for economic parameters, if you cannot look to eras before 1946 (if data don't go back that far), then it is important that you restrict your time-frame so that you only look at the first few decades after 1946, ignoring all recent decades in your analysis.
This is no different than a physicist exercising the practical wisdom of intentionally ignoring the time a rock spends in his hand before he lets go (when timing the rock's free fall). He doesn't start the timer before he let's it go.
He starts and stops the timer when the fall of the rock is not being interfered with.
Because business cycles take about 2.5 years in order for all adjustments to be made (leading indicator: interest rate increase 1.5 years before output peak; lagging indicator: peak investment 1.0 years after peak), the average of the best 3 consecutive years of recorded history is a good measure to obtain an accurate estimate of a natural rate.
To provide a contrast to the "worse" estimations of natural rates (those made under heavy economic intervention), here are some "better" estimations for the natural rates of economic parameters:
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Inflation (including recession years): 0.3% (1953-1955) ... [1]
Inflation (not including any recession years): 1.2% (1962-1964) ... [1]
Unemployment (U3) rate: 3.1% (1951-1953) ... [2]
Median Unemployment duration: 4.6 weeks (1968-1970) ... [3]
Mean Unemployment duration: 8.3 weeks (1968-1970) ... [4]
Real Productivity growth: 4.9% (1961-1963) ... [5]
Real Wage growth: 4.1% (1953-1955) ... [6]
Net Savings rate from gross income: 12.4% (1964-1966) ... [7]
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Economies should be compared to an objective standard (a natural rate).
When better estimates of natural rates are used rather than merely relying on "long-run averages" (which include eras with relatively heavy economic intervention), then it is clear that there is a large negative effect of the heavy economic intervention of the past several decades.
Inflation "shouldn't be" more than about 1%--and unemployment "shouldn't be" more than about 3%. Also, real productivity growth "should be" over 4% and real wage growth should at least approach 4%.
Each generation of US workers should be able to afford almost twice the stuff (almost twice the cars, houses, land acreage, etc.) that their own parents could afford to buy.
If these things all consistently occurred, then we'd have a healthy double-digit net savings rate (enough money available for net new investments). As it is, only 2.4% of income remains available for growth, which is not enough loanable funds to even sustain US living standards, let alone improve them.
To grow, our net savings "should be" 5 times as large as it currently is.
By not being good estimators of natural rates, contemporary economists increase the odds of broad acceptance and adoption of such pernicious notions as a "new normal"--which will only lead to economic collapse. The "boiling frog" analogy is appropriate here:
If you were sitting in a cauldron of water suspended over a fire and your thermometer slowly rose--but you kept comforting yourself by saying it is "natural and normal" to be sitting in water that is 120 degrees and rising--then you would not have the proper anxiety to become alarmed enough to jump out in time to save your own life, or to at least prevent being badly burned.
Economists do society a great disservice when they refer to long-run averages--including recent years, with at least 7 times the economic intervention of the past--as either "natural" or "normal."
Reference
[1] U.S. Bureau of Labor Statistics, Consumer Price Index: All Items in U.S. City Average, All Urban Consumers [CPIAUCNS], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/CPIAUCNS [use Edit Graph button at top-right to bring up the Modify Frequency function so as to change it from Monthly to Annual Average]
[2] U.S. Bureau of Labor Statistics, Civilian Unemployment Rate [UNRATE], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/UNRATE [use Edit Graph button at top-right to bring up the Modify Frequency function so as to change it from Monthly to Annual Average]
[3] U.S. Bureau of Labor Statistics, Median Duration of Unemployment [UEMPMED], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/UEMPMED [use Edit Graph button at top-right to bring up the Modify Frequency function so as to change it from Monthly to Annual Average]
[4] U.S. Bureau of Labor Statistics, Average (Mean) Duration of Unemployment [UEMPMEAN], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/UEMPMEAN [use Edit Graph button at top-right to bring up the Modify Frequency function so as to change it from Monthly to Annual Average]
[5] U.S. Bureau of Labor Statistics, Business Sector: Real Output Per Hour of All Persons [PRS84006092], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/PRS84006092 [use Edit Graph button at top-right to bring up the Modify Frequency function so as to change it from Quarterly to Annual Average]
[6] U.S. Bureau of Economic Analysis, Wage and salary accruals per full-time equivalent employee [A4401C0A052NBEA], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/A4401C0A052NBEA [divide nominal wage by CPI to obtain a real measure for each of the 3 years, then obtain rate of increase over the 3 years by taking the cube root of the ratio of "year 3/year 1" and then subtracting one to obtain the decimal rate of increase--ie, multiply it by 100 to obtain percentage increase]
[7] U.S. Bureau of Economic Analysis, Net saving as a percentage of gross national income [W207RC1A156NBEA], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/W207RC1A156NBEA