Tag Archives: Rate curves

Tips

Naughty naughty spreads

It happened to me (again!) yesterday. The curve spreads are naughty naught critters!

Let’s explain:

In some cases, the curve spread indicator (the small 1 or 2 on the left of the market quote) is sometimes bugged and does not work properly. Usually nothing to worry about as it is quite easy to see if there are spreads or not (just need to play with the combo box on the far right).

Unfortunately when you’re working on a new environment or with rates which source is not clear to you, they’re not always your first target.

So what happened? (I know this story is more thrilling than a Stephen King book (yep, just compared myself to Stephen King just like that))

Basically a curve was not calibrating and I followed my previous post steps to understand what was going on. Removing curve spreads, reducing the number of instruments (the quotes were ok). Finally it was calibrating to a crazy rate (-50%). Could not understand why, market quote was correct. Tried to overtype the zero rate and got a crazy market quote.

As the instrument had the market quote as a margin on the secondary I was suspecting that something was amiss there. The pricing maybe was reading incorrectly the margin. Started to look at other curves to see if the problem was there as well, but everything was ok.

So went back to my curve and somehow (imagine a spot light above my head) started to check my curve spreads! Et voila, eureka moment, there were convexity spreads (in the range of -50%). Zeroing them brought everything back inline, the curve calibrated ok, problem solved.

As usual with these kinds of problems, even if you’re proud to have solve the issue, you always feel bad not to have checked the guilty part first!

What about you dear reader? Any similar experience?

Tips

Rate propagation – Curve relationships

10 Comments

When working on Murex rate curves, one quickly faces the problem of curve relationships and what is called as rate propagation. Once understood, it seems very simple. But before you get to that “Eureka” point, it might be confusing. So let’s dig into it and hopefully bring you some “Eureka” moment!

First of all, rate propagation only makes sense when you are working with multiple curves in the same currency. The rate propagation determines how are the other curves going to move when one curve moves. The setting sits under the rates general settings and can take 3 different values:

– Keep market quotes constant (KMQC)
– Keep zero rates constant (KZCC)
– Keep market quotes constant/Impact sensitivities

The first one and the 3rd one have the same results when perturbing one curve but the 3rd one tries to show the sensitivities due to other curves perturbation. Effectively you should hesitate between the second and the third one, as the first one does not show you the right sensitivities.

In the mode KMQC, the rate curves are recalibrated after each perturbation. Let’s take the following example:

USD DISC
USD 3M
USD 6M

USD DISC has no dependency on other curves. It can self calibrate.
USD 3M depends on USD DISC to calibrate its swap pillars as they are estimated on USD 3M but discounted on USD DISC. USD 6M depends on the 2 other curves as it contains basis swaps estimated on both 3M and 6M curves and discounted on DISC curve.

Rate propagation mode : KZCC

In the mode KZCC, you basically assumes that if any rate changes, then the zero rates of the other curves do not change. So if your USD DISC curve changes, then the zero coupon rates of both USD 3M and USD 6M will remain the same. It means that the market rates of the USD 3M and 6M curves will change. Your ZC rate for the curves does not change, so the estimated rates will remain the same. But your discounting rate has changed (USD DISC has changed), so you need to change the fixed leg rate (aka your market quote) or your margin (basis swap market quotes) so that the NPV of the swaps remains 0.

Rate propagation mode : KMQC

In this mode, you assume that the market quotes remain the same when one curve is perturbed. So your ZC rates should be recomputed. Let’s see why! Using the same example as above and perturbing the USD DISC curve will yield the following:
– USD 3M ZC rates will change
– USD 6M ZC rates will change

When you’ve changed your USD DISC curve, the discounting rates will change. So in the case of your IRS in the 3M curve, the discounting rate will change, the fixed leg rate remains constant (Keep Market Quote Constant!), so your fixed leg has a different NPV. As such, you need to modify your estimation rate (USD 3m ZC) to reach a NPV of 0.
Similarly for the 6M curve, the 3M leg will have changed NPV, the 6M leg has different discounting rates, so you need to adjust the 6m estimation rates to keep a NPV of 0, so the 6M zero rates will change.

STOP there. There are more complexities that you can lay on top of these propagation modes but the above will always stay true: you need to maintain a NPV of 0 in every instrument in your curves and that’s the only way to do it.

1 more question:

I can’t reproduce the same behavior with manual shifting, why is it so?

What I wrote above is true and what should happen BUT sometimes the variation in values are actually quite small or 0. For instance, in KZCC, if your USD 3M curve is quite flat, then you won’t see much difference after the change in the discounting rates. Why? All flows fall on the same date for the fixed and floating leg. So you can sum both flows before applying the discount factor. If your estimation curve is flat, then prior to the shift of the discount rate, your sum of the 2 flows was already close to 0. As such, the impact of the discount factor is limited.

Rate relationships have changed a lot in the more recent versions with bugs and enhancements. So if there is something you can’t explain check with someone with more experience or a more recent version if you can.

Questions and comments are more than welcome!

Info

Funding curves

In the extension of the previous post, I’ll cover a bit the funding curves: what it means and how they’re being used.

  1. What are the funding curves?

A funding curve crystallizes the  funding spreads over the market rates for the bank. Usually you will find that these spreads are over the O/N rate and the funding curve is often in USD.

That curve represents the cost to the bank to fund their positions. When it needs to be expressed in different currencies the current approach is to ratio discount factors: Df(XXX funding curve)/Df(USD funding curve)=Df(XXX/USD basis curve)/Df(USD OIS curve). The assumption behind is that swap points are a constant.  So you end up with the discount factor you’re after (Df(XXX funding curve) as Df(XXX/USD basis curve)*Df(USD funding curve)/Df(USD OIS curve).

2.  How to set them up?

In Murex, this can be setup using the Automatic CSA curve setting. You’ll need to define a CSA category (such as No collateral) and attach the proper curve assignment to USD (assuming you’re using USD for funding).

3.  When are they used?

Trades can be collateralized or not. To be collateralized, they need to be covered by an agreement with your counterpart and in that case, any large market value for that transaction will trigger a margin call and thus limit the risk for both sides.
When the trades are not collateralized, this is when you want to use the funding curves as the bank is much more exposed and the returns expected are higher.

In terms of pricing, this also means that when trading with a non collateralized counterparty, the prices will be worse given the increased rates.

4.  Anything else? Risk management maybe?

This is where the funding desk comes into the picture. The role of that desk is to determine the funding spreads but also to manage the risk coming from these curves. For traders, they will also look at their portfolios as if all trades were fully collateralized BUT any trade with a counterparty with no agreement will effectively use the funding desk as an intermediary : the funding desk trades the same trade back to back, with the counterpart using the funding curves and with the trading desk using normal curves (OIS or basis curves).

In a nutshell, that’s what funding curves are about. As always, questions or comments are more than welcome!

Info

Rate curves

Today’s post is about rate curves, what they are, their purposes and where things are at the moment (Of writing this post)

  • What’s a rate curve?

The point of a rate curve is to produce discount factors (or discounting rates) in order to discount cash flows, estimate rates or capitalize a cash flow. In school, you tend to consider that there is an unique flat rate for all your discounting needs but in fact the rate is not constant over time and tend (it’s not a guarantee at all) to increase over time as your risk increases.

  • What’s inside a rate curve?

The main problem is that you need to find rates which are the best representation of where the risk free rates are sitting. So you’ll want to use the most liquid interbank instruments. For a standard curve, you’re usually looking at deposits on the short term, rate futures on the mid term and swaps on the longer term.

  • Is there more than one curve?

Sadly, yes. When I started people were using only one curve making risk management a hell lot easier. Then the cross currency basis curves appear. The expectation was that risk  is different for transactions which used more than a currency (FX deals and currency swaps for instance). So one would build a curve with liquid cross currency deals (today’s trend is swap points up to 1y, 18m and currency swaps on the longer run).
But it did not end there! Afterwards estimation curves were introduced as forecasting a 3m rate, 6m rate and 1m rate on the same curve was not returning correct results. Depending on the curve, the instruments are different but usually deposit for the first pillar as it also anchors properly the fixing rate for the day once published, futures or FRAs if available/liquid and basis swaps (also when available/liquid).
Finally, the curve that is maybe the most popular now: Overnight curve (Also called OIS Curve (for Overnight Index Swap). It is used for forecasting the overnight rate but also discounting many transactions (normally all collateralized ones, but I’ll detail that in another post). OIS curve is built using a depo for the O/N pillar and then either futures when available/liquid and OIS for the longer run.

While all these curves return a price which tends to be much closer to the market, they also make risk management a lot more complex especially as curves are related. So non rates traders are forced into this world and need to hedge their basis risk where before they were just looking at a single IR risk figure per currency.

Feel free to discuss further in the comments below or the forum, but it is a vast subject and worth actually multiple posts rather than just one.