Inflation gets all the attention. Turn on the financial news, scroll through social media, or have a conversation with almost anyone about the economy and eventually inflation comes up. How much does a house cost? What happened to grocery prices? Why are interest rates where they are? Why does everything seem so expensive? But there is another side of the price equation that we don't talk about nearly as much. Deflation.

That's partly because inflation is simply much more common in the modern U.S. economy. In fact, the Federal Reserve deliberately seeks a low, positive rate of inflation rather than zero inflation or deflation.

But deflation still matters.

And understanding it gives us another useful framework for thinking about the economy, debt, investing, and why falling prices aren't necessarily as wonderful as they sound.

What is deflation?

Let's start simple. Inflation occurs when the general price level of goods and services increases over time. Deflation is the opposite. It occurs when the general price level of goods and services falls over time.

Notice that I said the general price level.

A television getting cheaper is not deflation. Neither is gasoline dropping 20 cents per gallon or the price of eggs falling after a temporary spike. Individual products become cheaper all the time because of changes in supply, demand, technology, or competition.

True economic deflation is broader. Prices across the economy are persistently declining. And from the perspective of your money, this creates an interesting effect.

With inflation, the purchasing power of a dollar declines. If something costs $100 today and $103 next year, your dollar buys a little bit less.

During deflation, purchasing power moves in the opposite direction. If something costs $100 today but $97 next year, the same dollar buys more.

At first glance, that sounds pretty great. Who doesn't want things to get cheaper? Unfortunately, this is where deflation becomes much more complicated.

Why do we hear so much more about inflation?

There are a few reasons.

The first is simply that inflation is much more common in the modern U.S. economy.

The Federal Reserve's longer-run goal is 2% inflation. Importantly, policymakers are not trying to achieve 0% inflation. A small amount of positive inflation provides some buffer against outright deflation while supporting the Fed's broader goals of maximum employment and price stability.

Inflation also tends to dominate the conversation because it is incredibly visible.

You see it at the grocery store. You notice it when you buy a car. And you feel it when you pay your insurance bill, book a vacation, hire a contractor, or go out to dinner.

And psychologically, price increases hurt.

A slowing rate of inflation doesn't even necessarily feel good. If inflation falls from 8% to 3%, prices generally aren't falling. They're just increasing more slowly. The higher price level you already experienced doesn't magically reverse itself.

That's an important distinction between disinflation and deflation. Disinflation means prices are still increasing, just at a slower rate.

Deflation means the overall price level is actually falling.

So what causes deflation?

This is where we can go back to some pretty basic economics. There are several paths that can lead to falling prices.

1. Demand falls

Imagine an economy in which consumers suddenly become worried about their jobs and financial futures.

They stop buying cars. They delay renovations. Families cancel vacations. Businesses postpone expansion plans.

Demand drops.

Companies now have products and services they want to sell but fewer people willing to buy them. One way to attract those buyers is to lower prices.

If this happens broadly enough throughout the economy, it can contribute to deflation.

2. Supply or productivity increases

Deflation can also come from a much more positive source.

Suppose technological advances allow companies to produce dramatically more goods at a lower cost. Increased productivity can make products cheaper without necessarily signaling that anything is wrong with the economy.

We've seen versions of this in technology for decades.

Think about how much computing power you can buy today compared with decades ago. Better productivity and technology can create falling prices for specific goods while simultaneously improving living standards.

This is why simply saying “falling prices are bad” is too simplistic.

The cause matters.

3. Credit contracts

There's another mechanism that becomes especially important during financial crises.

Credit dries up. Banks become reluctant to lend. Consumers and businesses focus on paying down debt instead of borrowing more. The amount of money and credit circulating through the economy contracts.

That can reduce spending and asset prices, which can create additional downward pressure on the economy.

This is where we start getting into the concept of debt deflation.

When falling prices become a problem

Here's the strange thing about deflation.

From the perspective of one consumer buying one product, falling prices sound fantastic. From the perspective of an entire economy experiencing persistent falling prices, they can become dangerous.

Imagine that you want to buy a $50,000 car. But you believe that car will cost $47,000 next year.

Maybe you wait.

Now imagine a business considering a $1 million expansion. Management expects equipment, construction, and other costs to be lower next year while also worrying that its own products will sell for less.

Maybe the business waits too.

Multiply those decisions across millions of consumers and businesses and you can see the problem. Spending falls. Businesses generate less revenue. Lower revenue pressures profits. Companies may respond by cutting investment, reducing hiring, freezing wages, or laying off employees.

Those workers then become more nervous and spend even less. That decreases demand further. Prices fall again.

Now we have the beginnings of a deflationary cycle.

The Bank of Japan has described this type of feedback loop from its own experience with prolonged deflation: falling sales and profits can restrain wages and employment, which reduces household spending, putting still more downward pressure on prices and economic activity.

That's very different from your television becoming cheaper because manufacturers figured out how to make televisions more efficiently.

The really dangerous part: debt

For me, this is probably the most interesting part of deflation.

Deflation makes money more valuable. But your debt doesn't automatically shrink with prices.

Let's say you owe $500,000 on a mortgage. Your mortgage balance doesn't suddenly become $475,000 because prices and wages throughout the economy fell 5%. You still owe $500,000.

If your income falls along with the broader economy, however, that $500,000 debt has effectively become more burdensome relative to your income.

That's debt deflation.

Borrowers took out loans using yesterday's dollars and now have to repay those loans using more valuable dollars.

This can force households and businesses to sell assets, reduce spending, and pay down debt. Those actions can push asset prices and economic activity even lower.

And the cycle feeds on itself.

For physicians, this is particularly interesting because many of us carry significant debt at various stages of our financial lives. Student loans, mortgages, practice loans, and real estate debt all represent fixed nominal obligations.

Inflation generally reduces the real burden of fixed-rate debt over time. Deflation does the opposite.

What does deflation mean for regular people?

The answer depends enormously on your individual circumstances.

If you have a stable job, little debt, and a lot of cash, mild deflation can look pretty attractive. Your dollars are becoming more valuable.

The problem is that widespread deflation rarely occurs in an economic vacuum. If prices are falling because the economy is contracting, your job may become less secure. Wage growth may disappear. Businesses may stop hiring. Highly indebted households may struggle.

Someone who looks only at the price tag sees cheaper goods. Someone who looks at the entire economic picture sees why central bankers worry about persistent deflation.

There is also an expectations component.

Once people begin expecting prices to continue falling, their behavior can reinforce the trend. Japan experienced this problem for years, with expectations that prices and wages would not rise becoming increasingly entrenched.

Expectations affect behavior.

And behavior affects the economy.

What does deflation mean for investors?

This is probably where many readers' minds immediately go.

“If deflation happens, what should I invest in?” I would caution against jumping too quickly to that question. It's the same reason I don't recommend changing your entire investment strategy because you think inflation is coming, a recession is coming, or the stock market is about to crash.

Knowing what economic environments mean is useful.

Pretending that we can reliably predict when those environments will begin and end is something very different.

I've written before about why trying to identify and time the market cycle is so difficult. Even if you correctly identify a major economic trend, you still need to predict how markets will react and when that reaction will occur.

That's a lot of predictions.

Broadly speaking, severe deflation can be challenging for risk assets because it may accompany declining corporate revenues, weaker profits, recession, and financial stress.

High-quality bonds can potentially benefit because falling inflation often accompanies lower interest rates, which can increase the value of existing bonds with higher coupons. Cash also gains purchasing power during true deflation.

But none of this means I would build my entire portfolio around predicting deflation.

My own strategy remains boring by design: broadly diversified, low-cost index funds combined with bonds and direct real estate, all governed by a predetermined asset allocation and written financial plan. That is the same philosophy behind keeping and periodically updating my written financial plan.

I've also written more specifically about why bond funds can have a role in a physician's portfolio. Their purpose isn't to predict the next economic environment. It's to provide diversification and stability across many possible environments.

That's a big distinction.

Let's look at two historical examples.

Historical example #1: The Great Depression

If you want to understand why economists fear deflation, the Great Depression is the obvious place to start.

From the fall of 1930 through the winter of 1933, the U.S. money supply fell dramatically amid widespread banking failures. Prices declined substantially as well. But the falling prices weren't some incredible nationwide clearance sale.

They were part of an economic catastrophe.

The Federal Reserve's history of the Great Depression describes how falling prices increased real debt burdens, weakened spending, contributed to unemployment, and intensified financial distress.

Think back to our debt example.

Prices fall. Income falls. Asset values fall. Yet nominal debts remain. Borrowers struggle to repay those increasingly burdensome debts. Defaults hurt banks, which become less willing or able to lend. Credit contracts further.

The economy gets squeezed from multiple directions.

That is the ugly version of deflation.

Historical example #2: Japan's long battle with deflation

Japan gives us a very different example.

After its massive asset bubble burst around the beginning of the 1990s, Japan entered a prolonged period of economic stagnation. By the late 1990s, the country had fallen into sustained deflation.

But unlike the dramatic price collapse of the Great Depression, Japan's deflation was relatively mild.

It was just persistent.

The Bank of Japan has estimated that consumer prices declined by a total of about 4.1% during the 15 years from fiscal 1998 through fiscal 2012, or roughly 0.3% annually on average.

That doesn't sound particularly terrifying. And that's exactly what makes the example so interesting.

Businesses and households gradually adapted to an environment where prices and wages weren't expected to increase. Economic growth remained weak, interest rates approached their effective lower bound, and monetary policymakers struggled for years to generate sustained positive inflation.

Japan eventually used increasingly aggressive monetary policies, including near-zero interest rates and quantitative easing, in an effort to push the economy away from persistent deflation.

Japan shows us that deflation doesn't have to look like an economic apocalypse.

Sometimes it can simply become a persistent weight around an economy.

Why central banks actually want some inflation

This brings us to something that initially confused me when I first started learning about economics.

If inflation makes our money worth less, why would the Federal Reserve want any inflation at all? Why isn't the goal 0%?

One reason is that modest positive inflation creates a buffer against deflation.

Another is that central banks have more room to respond to recessions when nominal interest rates start above zero. Persistent deflation can make monetary policy more difficult because rates can run into their effective lower bound.

Moderate inflation also allows real wages and prices to adjust without requiring widespread nominal wage cuts, which can be economically and psychologically difficult.

None of this means high inflation is desirable.

It means that, from an economy-wide perspective, stable low inflation is generally preferable to either extreme.

That's an important nuance.

Deflation versus inflation: which should investors worry about?

Both. And neither. Let me explain.

Both inflation and deflation can create serious economic problems when they become extreme or persistent. They simply create different problems.

Inflation erodes purchasing power. Deflation increases purchasing power but can increase real debt burdens and contribute to economic contraction. Inflation can hurt holders of long-duration nominal assets. Deflation can hurt borrowers, businesses, workers, and owners of risk assets if it accompanies a severe downturn.

Understanding these relationships makes you a more informed investor.

But here's where I always come back to the same point.

Knowledge is useful. Prediction is dangerous.

I've lived through enough market environments now to know that there is always a compelling reason to change your investment plan. Inflation is too high. Interest rates are rising. A recession is coming. Stocks are at an all-time high. Valuations are too expensive. The market is crashing.

There will always be something.

That's why I've written about what doctors should do during a stock market downturn and whether you should keep investing when the stock market is already at an all-time high.

The answer keeps coming back to the same boring principles.

Create a financial plan. Set an asset allocation appropriate for your risk tolerance. Diversify. Invest consistently. Rebalance. Ignore predictions.

The bottom line on deflation

Deflation sounds simple.

Prices go down and your money becomes more valuable.

But like most concepts in economics, the second-order effects are what really matter.

Falling prices caused by innovation and productivity can be wonderful. Broad, persistent deflation caused by collapsing demand, contracting credit, or financial crises can create a vicious cycle of reduced spending, falling profits, unemployment, and increasingly burdensome debt.

History gives us examples of both severe, rapid deflation and mild, chronic deflation.

The Great Depression showed how destructive a deflationary spiral can become. Japan demonstrated how even modest deflation can weigh on an economy when it persists for years.

It's hard to imagine the U.S. economy suffering from deflation in our current inflationary environment. But it has happened in U.S. history, and it has occurred elsewhere in the world. So it's not something we can completely ignore.

As investors, we should understand these forces. But we don't need to predict them. That's an important difference and, in my experience, one of the biggest lessons in personal finance. Learn enough about economics to understand what's happening around you. Then build a financial plan strong enough that you don't need to know exactly what happens next.

What do you think? Do you worry about deflation? Do you think it could happen in the U.S.? What do you think could cause it? And most importantly, how does your financial plan account for it? Let me know in the comments below!