The whole return is a rate applied to a balance. What makes it unlike every other asset class is that the rate is set by the institution, can be changed at will, and you have agreed to that in advance.
10 min read · Level 1
Cash is the only asset class in this curriculum where the counterparty sets your return and is allowed to change it without asking, and I think the industry has been remarkably successful at making that feel normal. Imagine any other holding working this way: a bond issuer that could revise the coupon downward by letter, a tenant entitled to reduce the rent at their own discretion, a company that could decide your dividend is now a quarter of what it was and owed you no explanation. Each of those would be regarded as an outrageous arrangement, and each is precisely what a variable savings rate is. The reason nobody objects is that the capital is safe, and safety of capital is such a strong reassurance that it quietly absorbs every other complaint. That absorption is the thing to resist. A holder who accepts that the rate is somebody else's decision should at least behave like someone who has accepted it - which means checking the rate on a schedule rather than on a prompt, because no prompt is coming. The institution has no obligation to tell you that its own newer account pays more than yours, and it will not. In practice the discipline is twenty minutes a year with a calendar reminder, and the people who do it are not more sophisticated than the people who do not. They have simply stopped treating cash as a thing that looks after itself.
There is exactly one source of return here and it has no second component. No dividend, no appreciation, no rent, no claim on anybody's profits. Interest on a balance, and that is the list.
That makes the arithmetic short, and the only subtlety is how often the interest is added. Take 10,000 at a nominal 4.00% for one year:
Added once a year 10,000 x 1.04 = 10,400.00 Added monthly 10,000 x (1 + 0.04/12)^12 = 10,407.42 Added daily 10,000 x (1 + 0.04/365)^365 = 10,408.08
Effective annual rate: 4.0000%, 4.0742%, 4.0808%
Monthly compounding produced 7.42 more than annual. That is a small difference and it is worth knowing for one reason only: quoted rates are not always on the same basis, so two accounts advertising "4.00%" can pay slightly different amounts. Most markets require a like-for-like figure to be shown - an annual equivalent rate - and that is the number to compare.
Now the part that makes this class genuinely unlike the others.
The rate is set by the institution and can be changed at will. On a variable-rate account, the bank may raise or lower what it pays with notice, and the account terms you accepted say so. You are not consulted. There is no negotiation. The income from your largest guaranteed holding can halve while you are asleep, and the only thing that happens is a letter.
25,000 at 4.00% 1,000.00 a year 25,000 at 2.00% 500.00 a year
A fall of 500, which is 50.0% of the income, with the balance unchanged and nothing done by the holder.
The alternative is a fixed-term deposit: a rate agreed for a stated period, in exchange for giving up access. That converts the rate from something the bank can change into something contracted - and converts your liquidity from complete into scheduled. Which of those two you want is a question about when you need the money, not about which rate is higher.
What drives the rate the institution chooses is largely the central bank's policy rate, and that relationship is lesson three.
Because "the rate can change" sounds mild and behaves severely, and because the direction it moves in is exactly the direction that hurts.
Consider what the rate is tied to. Central banks raise policy rates when inflation is high and cut them when the economy weakens. So a saver's income tends to be highest when prices are rising fastest - which is when that income is worth least in real terms - and lowest when the economy is struggling, which is when many people most need it. The nominal return and the usefulness of the nominal return are not aligned, and that misalignment is structural rather than bad luck.
Then consider what a variable rate does to planning. Every other income-producing asset in this curriculum gives you something contractual or at least persistent: a bond's coupon is a legal obligation, a lease commits a tenant to a stated amount, even a dividend is a decision a board must actively take and is reluctant to cut. A variable savings rate is none of these. It is a number the institution publishes, revises when it chooses, and is under no obligation to justify.
So "I have 300,000 in savings producing 12,000 a year" is a sentence with a hidden clause. It means 12,000 at today's rate, for as long as today's rate lasts, which could be until next Tuesday. Anybody building a plan on cash income has to hold that uncertainty explicitly rather than treating the figure as a constant.
The fixed-term deposit removes it, at a price. Agreeing 4.00% for two years means 4.00% for two years regardless of what happens to policy rates - and it means the money is not available in between, or is available only on terms set out in the agreement. That is a real trade, and the mistake people make with it is almost always in one direction: they fix the money they might need and leave variable the money they certainly will not touch, because the decision gets made on which rate looks better rather than on when the money is required.
One last property, easy to state and easy to forget. Because the whole return is interest on a fixed balance, the return cannot be negative in nominal terms while the institution is solvent and the balance is within the guarantee. There is no year in which 10,000 becomes 9,200. That is genuinely different from every other class in this curriculum, it is the reason cash exists in a portfolio at all, and lesson five is about why nominal safety and real safety are not the same thing.
Educational, not personalised financial advice. Nothing in the Investor Academy is a recommendation to buy, sell or hold anything — what is right for you depends on your own circumstances and the rules where you live.
Two savers, both with 40,000, over a period in which the policy rate falls from 4.50% to 1.50%.
Saver one, variable-rate account. The account pays 3.60% at the start. As policy rates fall, the bank reduces it in steps, ending at 0.90%. Their income falls from 1,440 a year to 360 a year - a reduction of 75.0% - and at no point were they asked. Their money remained available throughout, every day, in full.
Saver two, three-year fixed-term deposit at 3.80%. Their income is 1,520 a year for three years and does not move. They also could not touch the money, and when a better use for it appeared eighteen months in, the choice was to leave it or to break the agreement on whatever terms it specified.
Read the two together rather than deciding which won. Saver two was right about rates and that is not the transferable lesson, because neither of them knew what rates would do. What is transferable is that they made different trades and each got exactly what their trade specified: one bought access and paid for it with uncertainty, the other bought certainty and paid for it with access.
The failure mode is choosing without noticing that a trade is being made. Somebody who fixes a deposit for five years because the rate is higher, and then needs the money in year two, has not been unlucky - they have bought an instrument whose single defining feature is that the money is unavailable, for a reason unrelated to whether the money would be needed.
And the small arithmetic from earlier has one honest use here. Comparing a 3.80% fixed rate against a 3.60% variable one is comparing two quantities where only the first is knowable, so the 0.20 percentage point difference - 80 a year on 40,000 - is not the thing being decided. The thing being decided is three years of access. Anyone who finds themselves weighing 80 against that has framed the question wrongly.
Treating a quoted rate as an income you can plan around. On a variable account it is today's rate, revisable without your agreement, and a fall from 4.00% to 2.00% halves the income with the balance untouched.
Comparing two rates quoted on different bases. Interest added daily, monthly and annually produce 4.0808%, 4.0742% and 4.0000% from the same nominal 4.00%. The gaps are small and the habit of checking which basis is quoted is not, because it is the same habit that catches much larger discrepancies in lesson four.
Choosing a fixed term on the rate rather than on the date you need the money. The defining feature of the instrument is that the money is unavailable. If that feature does not suit the money, no rate makes it suit.
Assuming a fixed rate is available for the asking on any amount. Fixed-term products carry minimums, windows in which they are offered, and terms that vary with the amount and the length - and the best ones are frequently withdrawn quickly.
Forgetting that the income is highest when it is worth least. Rates rise with inflation, so the years a saver receives most are the years that money buys least. Lesson five puts numbers on that, and it is the most important arithmetic in the subject.
The like-for-like figure accounts for how often interest is added. Two accounts both advertising 4.00% can pay 4.0000% and 4.0808% depending on the compounding basis - a small difference, and checking which figure you are looking at is the habit that also catches the much larger ones.
Money needed within weeks, money needed at a known date, money with no date at all. That sorting determines which instrument fits, and it has to happen first, because the highest rate on offer will always belong to the longest commitment and will always be tempting for money that cannot be committed.
One multiplication. On 25,000, a move from 4.00% to 2.00% takes 1,000 a year to 500. If that number matters to a plan, the plan is exposed to a decision somebody else makes, and that is worth knowing before it is made rather than after the letter arrives.
The terms will say: a number of days of interest forfeited, a fixed charge, or no access at all. These differ substantially between products and the difference is invisible on a rate table. It is the only part of a fixed-term agreement that you will care about if anything goes wrong, and it is written down in advance.
When choosing between a variable account and a fixed term, when comparing two advertised rates, and whenever cash income forms part of a plan that assumes it continues.
Do not fix money whose date of use you do not know, and do not treat the difference between two similar rates as the decision when one of them is variable - the uncertainty is larger than the gap and it is the thing you are actually choosing between.
A widely observed shape in retail banking is that an account opened at an attractive rate drifts downward over subsequent years while newer accounts at the same institution are launched at better ones. Nothing dishonest occurs: rate changes are notified as the terms require, and the notifications arrive alongside ordinary correspondence at a time when nobody is thinking about their savings. The holder's recollection of the rate stays anchored to whatever it was when they opened the account, sometimes years out of date, and because the balance never falls there is no event that prompts a review. The gap between what they believe they are earning and what they are earning widens without anything happening that feels like a change.
Your memory of your savings rate is probably the rate on the day you opened the account. Look up the current one rather than recalling it, and put the check in a calendar.
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