Non-strongly-convex smooth stochastic approximation with convergence rate O(1/n)

We consider the stochastic approximation problem where a convex function has to be minimized, given only the knowledge of unbiased estimates of its gradients at certain points, a framework which includes machine learning methods based on the minimization of the empirical risk. We focus on problems without strong convexity, for which all previously known algorithms achieve a convergence rate for function values of O(1/n^{1/2}). We consider and analyze two algorithms that achieve a rate of O(1/n) for classical supervised learning problems. For least-squares regression, we show that averaged stochastic gradient descent with constant step-size achieves the desired rate. For logistic regression, this is achieved by a simple novel stochastic gradient algorithm that (a) constructs successive local quadratic approximations of the loss functions, while (b) preserving the same running time complexity as stochastic gradient descent. For these algorithms, we provide a non-asymptotic analysis of the generalization error (in expectation, and also in high probability for least-squares), and run extensive experiments on standard machine learning benchmarks showing that they often outperform existing approaches

COMPULSORY VOTING AND GOVERNMENT SPENDING

In a recent issue of Economics and Politics Crain and Leonard (1993) described the effects of compulsory voting on government spending. The purpose of this paper is twofold. First, problems in Crain and Leonard's approach are identified. Their use of the median-voter model appears inconsistent and their choice of government consumption rather than government expenditure is questionable. Second, this paper begins an analysis of the composition of government expenditure. Cross-country data tentatively suggests that non-voters benefit relative to voters from government expenditure on health, housing and transfer payments while voters benefit from government expenditure on defense and economic services.

The Uneasy Case for the Flat Tax

There is a secret paradox at the heart of social contract theories. Such theories assume that, because personal security and private property are at risk in a state of nature, subjects will agree to grant Leviathan a monopoly of violence. But what is to prevent Leviathan from turning on his subjects once they have lain down their arms? If Leviathan has the same incentives as his subjects in the Hobbesian state of nature, he will plunder them more thoroughly than ever they plundered themselves in the state of nature. Thus the social contract always leaves subjects worse off, unless Leviathan can fetter himself. And how can Leviathan bind himself, if he can always impose confiscatory taxes or choke off trade through inefficient regulations? This Article suggests that schemes of progressive taxation, in which marginal tax rates increase with taxable income, may be seen as a useful incentive strategy to bribe Leviathan from imposing inefficient regulations. Income taxes give Leviathan an equity claim in his state's economy, and progressive taxes give him a greater residual interest in upside payoffs. Leviathan will then demand a higher side payment from interest groups to impose value- destroying regulations. Of course, progressive taxation imposes its own incentive costs, by reducing the subject's private gains. However, these costs must be balanced against the gains from correcting Leviathan's misincentives, and it may that such gains exceed the costs of progressive taxation.flat tax, Hobbes, political economy, Leviathan, regulation,mandates, constitutions, progressive taxation

Testing for Homogeneity with Kernel Fisher Discriminant Analysis

We propose to investigate test statistics for testing homogeneity in reproducing kernel Hilbert spaces. Asymptotic null distributions under null hypothesis are derived, and consistency against fixed and local alternatives is assessed. Finally, experimental evidence of the performance of the proposed approach on both artificial data and a speaker verification task is provided

Is Home Bias in Assets Related to Home Bias in Goods?

Obstfeld and Rogoff (2000) have reinvigorated an old literature on the link between home bias in the goods market and home bias in the asset market by arguing that trade costs in the goods market can account for the observed portfolio home bias. The key link between home bias in the two markets is the real exchange rate. Home bias in consumption implies a different expenditure allocation across countries, which leads to different inflation rates when measured in the same currency. This leads investors from different countries to choose different portfolios to hedge against inflation uncertainty. An older partial equilibrium literature argued that such hedge portfolios are not large enough to produce substantial home bias. We link the general equilibrium and partial equilibrium literatures and show that in both the resulting home bias in the equity market depends on a covariance-variance ratio: the covariance between the real exchange rate and the excess return on home relative to foreign equity, divided by the variance of the excess return. Empirical evidence shows that this ratio and the implied home bias are close to zero, casting significant doubt on a meaningful link between home bias in the goods and asset markets. General equilibrium models that conclude otherwise imply a covariance-variance ratio that is at odds with the data.

Predetermination of Currents and Field in Short-Circuit Voltage Operation for an Axial-Flux Permanent Magnet Machine

Risk of irreversible magnet demagnetization during short-circuit fault is analyzed in case of an axial-flux dual-rotor machine, using a three-dimensional finite-element method (3D-FEM). In order to validate the numerical model, calculated waveforms of the currents are compared with experimental results for short-circuit at low speeds. Then currents and magnetic flux density inside the magnets are computed for short-circuit at higher speeds in order to predetermine the maximum admissible speed for the machine

The low-frequency impact of daily monetary policy shocks

With rare exception, studies of monetary policy tend to neglect the timing of the innovations to the monetary policy instrument. Models which do take timing seriously are often difficult to compare to standard VAR models of monetary policy because of the differences in the frequency that they use. We propose an alternative model using MIDAS regressions which nests both ideas: Accurate (daily) timing of innovations to the monetary policy instrument are embedded in a monthly frequency VAR to determine the macroeconomic effects of high frequency changes to policy. We find that taking into account the timing of the shocks is important and can alleviate some of the puzzles in standard monthly VARs [e.g., the price puzzle]. We find that policy shocks are most important to variables thought of as being heavily expectations-oriented and that, contrary to some VAR studies, the effects of FOMC shocks on real variables are small.>Monetary policy ; Econometric models ; Prices

Corporate Yield Spreads: Default Risk or Liquidity? New Evidence from the Credit-Default Swap Market

We use the information in credit-default swaps to obtain direct measures of the size of the default and nondefault components in corporate spreads. We find that the majority of the corporate spread is due to default risk. This result holds for all rating categories and is robust to the definition of the riskless curve. We also find that the nondefault component is time varying and strongly related to measures of bond-specific illiquidity as well as to macroeconomic measures of bond-market liquidity.

Tourists’ motivations for visiting Kakum National Park, Ghana

Since travel motivations of tourists are becoming varied and complex, it has become necessary for tourist destinations to conduct regular investigations into this aspect of the industry to help meet the needs and desires of travellers. This study explores the travel motivations of tourists visiting Kakum National Park in Ghana. Data were collected from 342 tourists who completed their tour of the park between July and August 2015. The study reveals four main motivations of tourists who visited the park, namely adventure, education, escape and social interaction. Three distinct motivational segments were identified among the patrons, with those seeking for adventure and knowledge being the majority. It was concluded from the findings that tourists’ decisions to visit Kakum National Park were influenced by varied combinations of intrinsic and extrinsic motivational factors