Relation between interest rates and currency for a nation
What you are asking about is called Interest Rate Parity. Or for a longer explanation the article Interest Rate Parity at Wikipedia.  If the US has a rate of say zero, and the rate in Elbonia is 10%, one believes that in a year the exchange rate will be shifted by 10%, i.e. it will take 1.1 unit of their currency to get the dollars one unit did prior.  Else, you'd always profit from such FOREX trades.  (Disclaimer - I am not claiming this to be true or false, just offering one theory that explains the rate difference effect on future exchange rates. From Indian context, there are a number of factors that are influencing the economic condition and the exchange rate, interest rate etc. are reflection of the situation. I shall try and answer the question through the above Indian example. India is running a budget deficit of 4 odd % for last 6-7 years, which means that gov.in is spending more than their revenue collection, this money is not in the system, so the govt. has to print the money, either the direct 4% or the interest it has to pay on the money it borrows to cover the 4% (don't confuse this with US printing post 2008). After printing, the supply of INR is more compared to USD in the market (INR is current A/C convertible), value of INR w.r.t. USD falls (in simplistic terms). There is another impact of this printing, it increases the money supply in domestic market leading to inflation and overall price rise. To contain this price rise, Reserve Bank of India (RBI) increases the interest rates and increases Compulsory Reserve Ratio (CRR), thus trying to pull/lock-up money, so that overall money supply decreases, but there is a limit to which RBI can do this as overall growth rate keeps falling as money is more expensive to borrow to invest. The above (in simplistic term) how this is working. However, there are many factors in economy and the above should be treated as it is intended to, a simplistic view only.
I've always understood inflation to be linked to individual currencies, although my only research into the subject was an intro economics course in undergrad and I don't recall seeing why that would be the case.  I guess the basic principle is that currency traders are watching the printing presses and trading in exchange markets to the point that the exchange rates fall in relation to increases in money supply. There's probably something about the carry trade in there as well, but it's late and I took some medications, so someone else will have to carry that torch. I must admit I've not really paid attention to foreign currencies like HKD, but the proximity and political relationship with China probably greatly complicates your question, since part of the problem has been China's currency peg. The Swiss franc has appreciated quite a bit recently against the Euro as the European Central Bank (ECB) continues to print money to buy government bonds issues by Greek, Portugal, Spain and now Italy.  Some euro holders have flocked to the Swiss franc in an effort to preserve the savings from the massive Euro money printing.  This has increased the value of the Swiss franc.  In response, the Swiss National Bank (SNB) has tried to intervene multiple times in the currency market to keep the value of the Swiss franc low.  It does this by printing Swiss francs and using the newly printed francs to buy Euros.  The SNB interventions have failed to suppress the Swiss franc and its value has continued to rise.  The SNB has finally said they will print whatever it takes to maintain a desired peg to the Euro.  This had the desired effect of driving down the value of the franc. Which effect will this have long term for the euro zone? It is now clear that all major central bankers are in a currency devaluation war in which they are all trying to outprint each other.  The SNB was the last central bank to join the printing party.  I think this will lead to major inflation in all currencies as we have not seen the end of money printing.  Will this worsen the European financial crisis or is this not an important factor? I'm not sure this will have much affect on the ongoing European crisis since most of the European government debt is in euros. Should this announcement trigger any actions from common European people concerning their wealth? If a European is concerned with preserving their wealth I would think they would begin to start diverting some of their savings into a harder currency.  Europeans have experienced rapidly depreciating currencies more than people on any other continent.  I would think they would be the most experienced at preserving wealth from central bank shenanigans. First question:  Any, probably all, of the above. Second question:  The risk is that the currency will become worth less, or even worthless.  Most will resort to the printing press (inflation) which will tank the currency's purchasing power.  A different currency will have the same problem, but possibly less so than yours.  Real estate is a good deal.  So are eggs, if you were to ask a Weimar Germany farmer.  People will always need food and shelter. Stocks, gold, commodities, and physical real estate will not be affected by currency changes, regardless of whether those changes are fast or slow.  All bonds except those that are indexed to inflation will be demolished by sudden, unexpected devaluation. Notice: The above is true if devaluation is the only thing going on but this will not be the case.  Unfortunately, if the currency devalued rapidly it would be because something else is happening in the economy or government.  How these asset values are affected by that other thing would depend on what the other thing is.  In other words, you must tell us what you think will cause devaluation, then we can guess how it might affect stock, real estate, and commodity prices. The Hong Kong Dollar is based on the US dollar.  The Hong Kong central bank recognizes the US dollar as its reserve currency.  That is, the Hong Kong central bank keeps US dollars as its main reserve.  Not long ago the reserve currency of choice would have been gold.  Central banks of each country would need to have enough gold to back up any currency they issued.  Now central banks use the US dollar instead.  This is what is meant when people mention the US dollar being the reserve currency for most countries. From wiki regarding the HK dollar: A bank can issue a Hong Kong dollar only if it has the equivalent   exchange in US dollars on deposit. So you're assumption is correct: as the US Federal Reserve prints more money and that money finds its way to Hong Kong banks, the Hong Kong banks will be able to issue more Hong Kong dollars which will have an inflationary affect. What to do?  If you look around enough on this site you'll find some suggestions.  Here is one. I concur with the answers above - the difference is about the risk. But in this particular case I find the interest level implausible. 11% interest on deposits in USD seems very speculative and unsustainable. You can't guarantee such return on investment unless you engage in drug trade or some other illegal activity. Or it is a Ponzi scheme. So I would suspect that the bank is having liquidity problems. Which bank is it, by the way? We had a similar case in Bulgaria with one bank offering abnormal interest on deposits in EUR and USD. It went bust - the small depositors were rescued by the local version of FDIC but the large ones were destroyed. Your hypothetical money market account parallel basically nails it.  You understand exactly how the math works.  IRR computes a rate at which your money market account would have to pay interest in order to match whatever investment you are comparing to. That said, there are two major complicating factors to consider: Your hypothetical account would have to not only pay interest, but also lend money, at exactly the IRR rate.  In reality of course, it never happens this way.  You may be able to lend (invest) at x, but to borrow you're going to have to pay y.  IRR simplifies away that issue in order to give us a single number.  That number can be very handy for comparison to other competing hypothetical investments, but it does not capture that fundamental issue of lending rate vs. borrowing rate. An IRR calculation assumes implicitly that all cash flows, outgoing and incoming, are known and fixed; that is, risk-free.  It makes no allowance whatever for risk, and all investments have some level of risk.  Two investments that compute to the same IRR might have hugely different risk around their cashflows, and so not be a close decision at all.  To compare those investments, you might go to a measure like RAROC-- risk-adjusted return on capital.  But that's much harder, and more subjective, because it requires some numerical measurement of risk. The general idea is that if the statement wasn't true there would be an arbitrage opportunity.  You'll probably want to do the math yourself to believe me.  But theoretically you could borrow money in country A at their real interest rate, exchange it, then invest the money in the other country at Country B's interest rate.  Generating a profit without any risk.  There are a lot of assumptions that go along with the statement (like borrowing and lending have the same costs, but I'm sure that is assumed wherever you read that statement.) As Sean pointed out they usually mean LIBOR or the FFR (or for other countries the equivalent risk free rate of interest). I will just like to add on to what everyone has said here and will like to explain how various interest rates you mentioned work out when the risk free rate moves: For brevity, let's denote the risk free rate by Rf, the savings account interest rate as Rs, a mortgage interest rate as Rmort, and a term deposit rate with the bank as Rterm. Savings account interest rate: When a central bank revises the overnight lending rate (or the prime rate, repo rate etc.), in some countries banks are not obliged to increase the savings account interest rate. Usually a downward revision will force them to lower it (because they net they will be paying out = Rf - Rs). On the other hand, if Rf goes up and if one of the banks increases the Rs then other banks may be forced to do so too under competitive pressure. In some countries the central bank has the authority to revise Rs without revising the overnight lending rate. Term deposits with the bank (or certificates of deposit): Usually movements in these rates are more in sync with Rf than Rs is. The chief difference is that savings account offer more liquidity than term deposits and hence banks can offer lower rates and still get deposits under them --consider the higher interest rate offered by the term deposit as a liquidity risk premium. Generally, interest rates paid by instruments of similar risk profile that offer similar liquidity will move in parallel (otherwise there can be arbitrage). Sometimes these rates can move to anticipate a future change in Rf. Mortgage loan rates or other interests that you pay to the bank: If the risk free rate goes up, banks will increase these rates to keep the net interest they earn over risk free (= Δr = Rmort - Rf) the same. If Rf drops and if banks are not obliged to decrease loan rates then they will only do so if one of the banks does it first. P.S:- Wherever I have said they will do so when one of the banks does it first, I am not referring to a recursion but merely to the competitive market theory. Under such a theory, the first one to cut down the profit margin usually has a strong business incentive to do so (e.g., gain market share, or eliminate competition by lowering profit margins etc.). Others are forced to follow the trend. "It is important to distinguish between cause and effect as well as the supply (saving) versus demand (borrowing) side of money to understand the relationship between interest rates, bond yields, and inflation. What is mean by ""interest rates"" is usually based on the officially published rates determined by the central bank and is referenced to the overnight lending rate for meeting reserve requirements.  In practice, what the means is, (for example) in the United States the Federal Reserve will have periodic meetings to determine whether to leave this rate alone or to raise or lower the rate.  The new rate is generally determined by their assessment of current and forecast national and global economic conditions and factors in the votes of the various Regional Federal Reserve Presidents.  If the Fed anticipates economic weakness they will tend to lower and keep rates lower, while when the economy seems to be overheated the tendency will be to raise rates. Bond yields are also based on the expectation of future economic conditions, but as determined by market participants.  At times the market will actually ""lead"" the Fed in bidding bond prices up or down, while at other times it will react after the Fed does.  However, ignoring the varying time lag the two generally will track each other because they are really the same thing.  The only difference is the participants which are collectively determining what the rates/yields are. The inverse relationship between interest rates and inflation is the main reason for fluctuating rates in the first place.  The Fed will tend to raise rates to try to slow inflation, and lower rates when it feels inflation is too low and economic growth should be stimulated.  Likewise, when the economy is doing poorly there is both little inflationary pressure (driving interest rates down both in terms of what savers can accept to keep ahead of inflation and at) and depressed levels of borrowing (reduced demand for money, driving down rates to try to balance supply and demand), and the opposite is true when the economy is booming. Bond yields are thus positively correlated to inflation because during periods of high inflation savers won't want to invest in bonds that don't provide them with an acceptable inflation adjusted yield.  But high interest rates tend to have the effect or reining in inflation because it gets more costly for borrowers and thus puts a damper on new economic activity. So to summarize," Yes - it's called the rate of inflation. The rate of return over the rate of inflation is called the real rate of return.   So if a currency experiences a 2% rate of inflation, and your investment makes a 3% rate of return, your real rate of return is only 1%. One problem is that inflation is always backwards-looking, while investment returns are always forward-looking. There are ways to calculate an expected rate of inflation from foreign exchange futures and other market instruments, though. That said, when comparing investments, typically all investments are in the same currency, so the effect of inflation is the same, and inflation makes  no difference in a comparative analysis.  When comparing investments in different currencies, then the rate of inflation may become important. Thanks. It has taken me some time to understand how all this works, and there are still many gray areas I want to understand further.  The Fed interest rate is the rate charged by banks to loan to each other to balance overnight reserves but only using the reserves they hold at the Fed. That adds no new money to the system, but increases the money multiplier a little since perhaps more loans can be made.   Basically one bank with excess reserves can loan to another bank that needs reserves. The Fed injects no money here, only sets the rate for banks to do this with each other.  When the Fed buys securities that effectively adds that many more dollars into circulation, which then gets hit by the money multiplier, adding a lot of new liquidity.  I think historically the latter tracks increases in the money supply much better than the former. I think the St. Louis Fed has records online for all this dating back to the 1940's or so. This is very insightful, I think. As an open question, consider what *downside* a nation (or bank) has to acknowledging bitcoin or other cryptocurrencies. Obviously nations may lose some monetary control by endorsing bitcoin, but I don't know if there's much of a downside for banks considering bitcoin's easy conversion in to USD.   If anything, I feel like most of the problems for banks surrounding cryptos would be regulatory. Basically, they all do. The relationship is much more dynamic with stocks but corporate financing costs increase, return requirements increase (risk free rate goes up). Same with real estate. Commodity demand is correlated with economic activity, which is correlated with interest rates, although not perfectly. The most important factor is, a higher risk free rate increases the discount rate, which reduces asset values Not to be a jerk, since I'm learning about options myself, but I think you have a few things wrong about your tesla put postion.  First, assuming it was itm or atm within a week of strike it would maybe be worth $12-15, I glanced at the 11/10 put strikes ~325 trades for $12.65 https://www.barchart.com/stocks/quotes/TSLA/options?expiration=2017-11-10  The closer it gets to expiry theta decay reduces put value significantly, the 325's that expire tomorrow are only worth $2.60.   Expecting TSLA to drop from 325 to 50 a share by Jan has a .006% chance of occuring according to the current delta. It's a lottery ticket at best.  _____ Lastly the $50 price is the expected share price at the date of expiry. The price you pay is 57c for the options. So in order to get to your 494k number TSLA would need to decline $50 dollars to a price of 275 a share. You wouldn't want to buy 50 dollar puts, just the 275 puts, provided it declines very quickly.   EDIT: I was looking at the recent expiration to get an idea of atm or itm prices, since it's not like you would hold to expiration. Also the Jan has a 0.6% chance of hitting 50, not .006%. That said what I've noticed when things start to slide is that puts have a weird way of pricing themselves. For example when something gradually goes up all of the calls go up down the chain through time frames, but puts do not in the same fashion. Further out lower priced puts won't move nearly as much unless the company is basically headed for bankruptcy.