Why Your Savings Are Losing Value and How to Calculate Real Returns on Deposits

Introduction

Did you know your savings can lose value even when your account balance is growing? Many people fall into the trap of nominal money illusion, unknowingly allowing inflation to erode their wealth. In an era where deposit interest rates often fail to outpace rising prices, simply saving is no longer enough. It is time to move past the illusion of safety and master the math behind the purchasing power of your hard-earned money. Learn the mechanisms that are depleting your capital and how to overcome them.

Why Your Financial Intuition Fails During Persistent Inflation

Most retail investors fall victim to the endowment effect (or the money illusion), which leads us to treat our nominal account balance as the primary measure of our wealth. Seeing the same or a slightly higher figure in our banking app compared to a year ago provides a false sense of security. This is a dangerous delusion. In reality, during periods of heightened price dynamics, your money is not "sitting safely"—it is being actively eroded by the invisible tax that is inflation.

The "Safe Deposit" Trap

Analyzing data from 2022–2025 reveals a brutal gap between the purchasing power of money and what banking offers. At the peak of 2022, when CPI inflation in Poland exceeded 18%, standard term deposits offered an average of 6% to 8% per annum. Even after accounting for the 19% capital gains tax (the Belka tax), the real rate of return was deeply negative. This means that every zloty deposited in a bank in 2022 allowed you to purchase goods worth over a dozen percent less 12 months later than at the time of deposit.

The situation is further complicated by the phenomenon of inflation stickiness, which is the tendency for prices to remain high even after the initial supply shocks have faded. Between 2023 and 2025, we observed the persistence of core inflation, which, after excluding the most volatile food and energy prices, remained significantly above central bank inflation targets. While your savings were "working" for a meager 4–5% on a deposit, the average basket of consumer goods was rising at a rate that permanently lowered your standard of living. If you do not learn to convert your nominal gains into real purchasing power, your savings will become nothing more than a "deposit for losses."

The Liquidity Trap in Personal Portfolios

Financial liquidity is the ability to cover liabilities immediately without sacrificing the value of your assets. While it serves as the cornerstone of financial security, it becomes a trap in an environment of elevated inflation. An excessive drive to keep cash "on hand" leads to the accumulation of idle capital that fails to generate returns and systematically loses purchasing power.

The Mechanism of Opportunity Cost in Practice

The most compelling evidence of the destructive impact of a "safe" strategy is an analysis of opportunity cost. Let’s assume you have 50,000 PLN sitting in a standard savings account with an annual interest rate of 4%. With annual inflation (CPI) at 5%, the real return on your investment is negative. Mathematically, after one year, your nominal capital will grow to 52,000 PLN; however, in real terms, accounting for inflation, its purchasing power will drop to approximately 49,524 PLN. You are effectively losing 476 PLN per year, essentially paying a "liquidity tax."

At the same time, alternative variable-income instruments, such as EDO treasury bonds (inflation-indexed) or a diversified portfolio of corporate bond ETFs, could generate returns exceeding the CPI index. Holding too much of your wealth in liquid assets during a period of high interest rates represents a conscious choice to forgo protection against value erosion.

This problem stems from a psychological aversion to risk, which leads investors to view cash as a "safe" asset. In reality, cash is the riskiest component of a long-term portfolio. Every thousand PLN held in cash beyond the level of a necessary emergency fund (typically 3–6 months of living expenses) is capital that does not participate in wealth creation, but instead actively loses value due to inflation. Portfolio optimization, therefore, requires moving beyond the high-liquidity mindset in favor of instruments with higher real return potential.

How to calculate your real post-tax rate of return

In the world of finance, the figure shown on your bank statement is merely an illusion. The key parameter that determines whether your capital is genuinely growing or simply disappearing at a slower rate is the real rate of return. To determine it, you must "cleanse" your nominal profit of the two primary capital destroyers: taxes and the loss of purchasing power.

The mathematics of real profit: Formula and example

To calculate your real profit, you must apply a mathematical adjustment based on the Fisher effect, which links nominal rates of return with expected inflation. The formula for the real rate of return (R) is as follows:

R = [(1 + post-tax nominal rate) / (1 + inflation rate)] - 1

Let’s break this down using a bank deposit as an example. Suppose you open a deposit with a 6% annual interest rate. The first step is to subtract the Belka tax, which is the 19% flat tax on capital gains. Your net profit (post-tax) is therefore: 6% * (1 - 0.19) = 4.86%.

If, during the same period, the official inflation rate (CPI index) is 5%, we plug the data into the formula: R = [(1 + 0.0486) / (1 + 0.05)] - 1 R = [1.0486 / 1.05] - 1 R ≈ 0.9986 - 1 = -0.0014, or -0.14%.

The result is brutal: despite a theoretical interest rate of 6%, your purchasing power has actually fallen by 0.14%. The nominal rate of return misleads investors, suggesting a profit where, in reality, capital erosion is occurring. In times of high inflation, even safe instruments like treasury bonds or term deposits rarely generate a positive result once the 19% tax is taken into account. The key to portfolio management is understanding that every percentage point of inflation above your net interest rate represents a direct loss of your wealth.

What the history of Polish interest rates teaches us about capital preservation

Analyzing the NBP reference rate chart from the last decade reveals a brutal truth about passive saving. Between 2015 and 2019, with rates held steady at 1.5%, the Polish banking system offered deposit interest rates that frequently hovered between 1–2%. When accounting for CPI inflation, the real return on deposits during this period was negative. At the time, interest rate risk was largely ignored, as low volatility lulled retail investors into a false sense of security, conditioning them to view bank deposits as a safe—albeit capital-eroding—haven.

Economic cycles and the deposit trap

The current "higher for longer" regime, characterized by a reference rate of 5.75% (as of 2024), is merely a phase rather than a permanent state. The economic cycle demonstrates that periods of restrictive monetary policy have a finite lifespan, dictated by GDP performance and the MPC's (RPP) inflation targets. History teaches us that a phase of high rates is typically followed by a sharp downward pivot, often forced by an economic slowdown.

A strategy based exclusively on deposits is defenseless against this dynamic. Once the MPC begins a rate-cutting cycle, the yields on deposits and savings accounts will react with a lag but will inevitably fall, leaving savers with low interest rates in the face of persistent market price volatility. Fixed-income instruments, such as EDO treasury bonds (inflation-indexed) or retail fixed-rate bonds, represent a more resilient alternative; however, even these require active portfolio management. Relying solely on short-term deposits is a classic "buying at the top" mistake, which, in the long run, leads to the erosion of purchasing power. Understanding that NBP reference rates are a variable rather than a constant is crucial for protecting the real value of capital over a decadal horizon.

Building an inflation-proof portfolio in the Polish market

Effective portfolio diversification in the face of the chronic loss of the Polish zloty’s purchasing power requires abandoning strategies based solely on bank deposits, as their interest rates rarely keep pace with real CPI inflation. To preserve the value of your capital, you must shift your focus toward assets whose returns are correlated with the rising prices of goods and services.

The foundation: inflation-indexed bonds (EDO)

The safest tool for capital preservation in the Polish reality is the EDO (ten-year) Treasury bond. Their structure is based on a margin (e.g., 1.25–1.50 percentage points) added to the current inflation rate published by Statistics Poland (GUS). In practice, this means that while you receive a fixed interest rate in the first year, your return for the following nine years is automatically "pegged" to the official inflation reading. It is the only debt instrument in Poland that guarantees that the real value of your money will not plummet over the long term.

A defensive portfolio should also include real assets, which have historically preserved value during economic downturns. Physical gold should account for 5–10% of your portfolio. Do not view it as a dividend-generating investment, but rather as an "insurance policy" for your wealth in the event of a currency crisis or high cost-push inflation.

This should be complemented by dividend stock ETFs, which provide exposure to global companies paying regular returns. By selecting Dividend Aristocrats funds, you gain protection against inflation driven by the pricing power of strong corporations capable of passing production costs on to the end consumer. This portfolio structure—based on sovereign debt, precious metals, and cash-flow-generating equities—creates a bulwark that effectively secures the purchasing power of your savings over a 5–10 year cycle.

How to manage liquidity in your daily household budget

Effective capital management requires establishing a liquidity hierarchy—a structural distribution of funds based on their potential time of use. A common mistake that leads to the erosion of the real value of savings is keeping all capital in low-interest checking accounts. To avoid this, you must implement purpose-driven budgeting by dividing your finances into three independent silos.

Strategic asset allocation

The first pillar is your emergency fund, covering 3 months of living expenses. These funds should be placed in high-liquidity instruments, such as term deposits or savings accounts, where the nominal interest rate (e.g., 5-6% per annum) minimizes the effects of inflation while posing zero risk of capital loss.

The second level covers short- and medium-term goals (e.g., home renovation, down payment). The optimal tools here are government bonds (e.g., EDO or COI), which offer inflation protection, maintaining the real purchasing power of money over a 3-10 year horizon. The third level, retirement capital, requires exposure to the capital market. Instruments such as broad-market ETFs (e.g., S&P 500 or MSCI World) have historically provided returns that outperform inflation over decades.

Liquidity management relies on the cyclical revision of these silos. If your household budget shows a surplus, it should not be allowed to "sit idle" in your checking account. Instead, once your 3-month liquidity buffer is secured, surpluses must be automatically redirected into your investment silo. Tools like YMH facilitate this process by enabling precise expense categorization and automated saving. The key is to separate money intended for daily living from capital meant to work for you in the long term. Only this approach allows you to avoid the "liquidity trap," where the loss of cash purchasing power becomes the primary cost within your household budget.

Summary

Protecting your capital in today's economic landscape requires moving beyond the passive habit of holding funds in a checking account. The key is understanding that idle money loses value faster than you might think. By consciously managing liquidity, diversifying your assets into the right investment silos, and utilizing solutions like YMH, you can gain better control over your household budget. Moving from illusory safety to genuine capital preservation is the process that will secure your standard of living for years to come.