Efficiency of cryptocurrencies : will arbitrage opportunities continue?

Cryptocurrencies are increasingly popular among investors and consequently receive rising attention, not only from the public but also from researchers. However, there remain many unsettled questions like whether cryptocurrencies are weak-form efficient. If they were, this would mean that technical trading, the most widely used trading strategy by retail traders, does no longer yield abnormal returns. This paper adds to the current literature by analysing the development of efficiency in Bitcoin and Ether over a time horizon from 2010 to 2022. I take these two cryptocurrencies as representatives of the overall cryptocurrency market since together they have a market share of over 60%. Using multiple efficiency tests, I build an efficiency index to track the development of efficiency of the analysed cryptocurrencies. Through a dynamic rolling window analysis and the split among several representative subsamples, I conclude that Bitcoin and Ether become more efficient over time. For both cryptocurrencies, this increase in efficiency is positively correlated with an increase in liquidity. Comparing these results to the exchange rate of the Euro to the US-Dollar, the cryptocurrencies show a higher level of efficiency. This is not surprising considering that there is no central authority intervening to regulate the market.Criptomoedas são cada vez mais populares entre investidores, e como consequência recebem mais atenção não só pelo público, mas também por investigadores. No entanto, ainda permanecem muitas questões, tais como se criptomoedas são eficientes na forma fraca. Se são, isto significaria que Technical Trading, a estratégia de trading mais usada por traders de retalho, não é capaz de gerar retornos anormais. Este papel acrescenta há existente literatura analisando o desenvolvimento da eficiência em Bitcoin e Ether ao longo de um período desde 2010 a 2022. Eu uso estas duas criptomoedas como representantes do mercado em geral pois, combinadas têm uma quota de mercado superior a 60%. Usando múltiplos testes de eficiência, eu construo um índice de eficiência, com o qual eu acompanho o desenvolvimento da eficiência das criptomoedas analisadas. Através de uma análise dinâmica com uma janela rolante e uma divisão entre várias subamostras representativas, eu concluo que Bitcoin e Ether tornam-se mais eficientes ao longo do tempo. Para ambas criptomoedas, este aumento em eficiência está positivamente correlacionado com um aumento em liquidez. Comparando estes resultados com o câmbio do Euro para o USD, estas criptomoedas exibem um nível de eficiência mais elevado. Isto não é surpreendente considerando que não existe nenhuma autoridade central a regular o mercado

The effects of radio-frequency lesions of the nucleus accumbens on d-amphetamine induced locomotor and rearing behaviors in rats/

A larqe body of evidence supports the conclusion that mesolimbic dopaminerqic neurons, in particular those that innervate the nucleus accumbens (n.ACC), are important for the expression of d-amphetamine stimulated locomotor behavior (ASLB) . However, one recent study has contradicted this conclusion, reporting that bilateral lesions of the n.ACC fail to block ASLB. It appears that this study contains a methodoloqical flaw in that it employed a qeneral measure of activity which did not distinquish between locomotion and rcaring. In the present study, we used observer ratinqs of videotaped responses to determine the seperate effects of 2.0 mq/kq d-amphetamine on locomotion and rearinq in rats with either sham or radio-frequency lesions of the n.ACC. It was found that n.ACC lesiongs blocked the locomotor stimulation, but not the increased rearinq, which follows d-amphetamine administration. Additionally, the time spent engaging in stereotyped behaviors followinq administration of a hiqh dose of the donamine agonist apomorphine was not affected by the lesion. These results support the general conclusion that dooaminemic terminals in the n.ACC are important for the expression of ASLB, and further suggest that d-amnhetamine-stimulated locomotion and rearing are mediated throuoh different neural suibstrates

Taking the initiative: the European Parliament and EU arms export controls

The Council of the European Union and the member states have failed to counter the substantial weaknesses of EU arms export controls. It is now the European parliament’s turn to take the debate forward by developing its own concept of restrictive EU arms export controls. A communitisation of arms export controls under the authority of the European Commission is unrealistic and undesirable. While it would offer the possibility of formal sanctions, it might lead to an even less restrictive control system than the existing one. Instead, the European parliament should build on the regulatory potential of social sanctions and naming and shaming-effects within the current division of competencies. Arms exports to non-EU countries should not be permitted on principle. An exemption to this exclusion would have to be specifically justified. Therefore, member states should agree on a ‘White List’ of recipient countries for European arms, which are assessed unanimously as acceptable. If member states nevertheless grant licences to non-EU countries that are not listed on the White List, they would be obliged to justify these decisions on COARM or Council level. To stimulate the debate on these instruments, the European parliament itself should work on a ‘White List’ and assess the member states’ export practices against this background. The European parliament should create a subcommittee on arms export controls to discuss improvements of EU arms export controls and to act as a supervisory body. The subcommittee would publish an annual report assessing member states’ export practices. An advisory body that ensures exchange between members of the European parliament, national parliamentarians and societal actors should assist this subcommittee

Set Covering with Our Eyes Wide Shut

In the stochastic set cover problem (Grandoni et al., FOCS '08), we are given a collection $\mathcal{S}$ of $m$ sets over a universe $\mathcal{U}$ of size $N$, and a distribution $D$ over elements of $\mathcal{U}$. The algorithm draws $n$ elements one-by-one from $D$ and must buy a set to cover each element on arrival; the goal is to minimize the total cost of sets bought during this process. A universal algorithm a priori maps each element $u \in \mathcal{U}$ to a set $S(u)$ such that if $U \subseteq \mathcal{U}$ is formed by drawing $n$ times from distribution $D$, then the algorithm commits to outputting $S(U)$. Grandoni et al. gave an $O(\log mN)$-competitive universal algorithm for this stochastic set cover problem. We improve unilaterally upon this result by giving a simple, polynomial time $O(\log mn)$-competitive universal algorithm for the more general prophet version, in which $U$ is formed by drawing from $n$ different distributions $D_1, \ldots, D_n$. Furthermore, we show that we do not need full foreknowledge of the distributions: in fact, a single sample from each distribution suffices. We show similar results for the 2-stage prophet setting and for the online-with-a-sample setting. We obtain our results via a generic reduction from the single-sample prophet setting to the random-order setting; this reduction holds for a broad class of minimization problems that includes all covering problems. We take advantage of this framework by giving random-order algorithms for non-metric facility location and set multicover; using our framework, these automatically translate to universal prophet algorithms

Can Buyers Reveal for a Better Deal?

We study small-scale market interactions in which buyers are allowed to credibly reveal partial information about their types to the seller. Previous recent work has studied the special case where there is one buyer and one good, showing that such communication can simultaneously improve social welfare and ex ante buyer utility. With multiple buyers, we find that the buyer-optimal signalling schemes from the one-buyer case are actually harmful to buyer welfare. Moreover, we prove several impossibility results showing that, with either multiple i.i.d. buyers or multiple i.i.d. goods, maximizing buyer utility can be at odds with social efficiency, which is a surprising contrast to the one-buyer, one-good case. Finally, we investigate the computational tractability of implementing desirable equilibrium outcomes. We find that, even with one buyer and one good, optimizing buyer utility is generally NP-hard, but tractable in a practical restricted setting