Tricking your optimiser

I have found that optimisers (R’s optim to be precise) are sometime unstable. Not in a numerical sense, but in a more practical sense, i.e. choking on certain inputs (I wasn’t able to figure out when exactly) and in the end crashing, without the possibility of recovery or error-processing. Which is quite bad, when you’re in the mid of some long calculations, e.g. a Monte-Carlo experiment. I found that optim’s standard method, Nelder-Mead, was unsusceptible to such crashes (Please, geeks, explain me why!). But with Nelder-Mead, you cannot use parameter constraints, so you have to formulate your optimisation problem in an unconstrained way. Here are some of my tricks.

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Democracy in the time of postfacts

Some time ago, an op-ed in a German newspaper (Die Zeit, I believe) decried the use of the term „postfact“ and suggested we should call the bullshit uttered by the Trump administration, the Brexit campaign and others as just what it is: lies. Well, certainly, postfacts are lies, but there is a subtle distinction. Post-facts create their own, subjective version of reality – or “truth” – whereas lies contradict the objective truth. This distinction lays bare a fundamental problem of our democratic way to organise government. It does not really matter, whether Donald Trump or Nigel Farage actually believe the nonsense they utter, but it matters that their voters believe it, because it fits their view on the world.

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One Swallow Doesn’t Make A Summer

Today Eurostat announced that the Euro area’s inflation rate (as measured by the HICP) has reached two per cent in February (see press release here: While seems finally some good news for the crisis-battered Euro area, it actually isn’t. Here’s why. Continue reading One Swallow Doesn’t Make A Summer

On ifo’s accountability bonds

In a recent press statement, ifo’s President Clemens Fuest argues for second-tier “accountability” bonds that would allow debt above the current limits of the Maastricht criteria, but with strings attached. From the statement:

Fuest and Becker propose that states only be allowed to finance 0.5 percent of their annual economic output with normal bonds. Should they run higher deficits, the excess debt should be subordinate i.e. it will only be repaid after other debts, must not be bought by the ECB, and should also only be held by banks with higher equity cover.

He continues to argue that such bonds would have far higher interest rates than regular bonds, thus discouraging states from using them to much. Continue reading On ifo’s accountability bonds

I thought we were past that

In a recent interview with the FT, Peter Navarro, an advisor to Donald Trump claimed the undervalued Euro to be an implicit Deutsche Mark and would benefit only Germany at the expense of our fellow Europeans and, of course, the US.

Hoo boy.

OK, I know that facts are not a particular strength of the new US government, but still, at least the assessment of the situation is correct: The Euro is probably undervalued vis-a-vis the Dollar, if you believe in The Economist’s Big-Mac-Index and thus in purchasing power parity. Given the more robust labour market and the recent monetary tightening of the Fed as compared to the Eurozone’s mess and still ultra-loose monetary policy by the ECB, the claim that the Euro is undervalued isn’t really a stretch.

Also true, undervalued currencies usually, ceteris paribus, benefit exporters of which Germany has a lot. But most of our exports go to Europe, i.e. the claim that Germany would benefit unfairly from the undervalued Euro is not as strong as you may think. In 2015 (oh facts again!), only 9.5% of our exports go to the US ( How exactly our exports to other Eurozone-countries are subject to the (external!) exchange rate is beyond me.

But for the sake of the argument, let’s assume for a second that Germany is benefitting unfairly. The obvious remedy for this would be an appreciation of the Euro vis-a-vis the Dollar, and to do this the ECB should stop its ultra-loose monetary policy and start raising interest rates better sooner than later. Wait, what? Yes, this is basically what Jens Weidmann and Wolfgang Schäuble demand for quite some time now. The allegations that Germany would keep the exchange rate towards the Dollar artificially low is nonsense, at best. And even if, there are some compelling arguments of why the ECB has adopted an ultra-loose monetary policy: weak labour markets in the south, under-capitalised banks, over-indebted governments, etc. Better export opportunities for Germany are merely a side-effect. We can talk about whether the ECB’s policy is adequate or what exactly drives Germany’s exports (non-substitutability perhaps?) or whether purchasing power parity holds, but going back to mercantilist thinking of the past fits the US goverment’s economic thinking: they are not thinking at all.

Repaying Germany’s debt is a good plan, but there is a better one

Politics discuss what to do with Germany’s federal budget surplus of a bit over €6bn. Wolfgang Schäuble, the finance minister, wants to repay some of Germany’s outstanding debt, which is generally a good idea. First, Germany violates a Maastricht criterion by having debt of more than 60 per cent of its GDP and as we have seen in the European debt crisis, high public debt can at times be very dangerous.

Now, usually me as a “fiscal hawk” would agree with Mr Schäuble. But given Germany’s robust growth (1.9 per cent in the last quarter), the general improvement of the federal budget and the fact that we fall behind schedule in investment (see slide 5 of the above presentation by the finance ministry), I would rather suggest to keep the €6bn in the coffers and try to focus more investment (e.g. broadband, infrastructure and education) to bring the money where it is actually needed.

Deutsche Bank and the curious case of surprisingly low fines

After some two weeks of falling stocks, talk about a merger with Commerzbank, musings about bailouts, bashing of its investment banking arm and reassuring statements by all sort of politicians (and competitors!), Deutsche Bank yesterday made a somewhat impressive rebound at the stock markets. Preceding was a rumour, that it may face fines only worth €5.4b instead of the previously floated €14b.

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Some thoughts around Brexit

On Friday morning I was shocked, probably just like everybody else. In the course of the day, that shock became anger. As such, I refrained from writing about Britain’s imminent quitting the European Union, fearing that it would only be a rant. Over the weekend, I have spoken with people about it, heard different opinions, read analyses, laughed about jokes and sorted my thoughts. This post might still be somewhat rant-ish, but very much less than if I had written it on Friday or Saturday (luckily I was busy otherwise). I will not deal with Brexit as such, there are already enough analyses about this disaster, but I will focus more on related thoughts about society, democracy and politics.
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