ESPRIT for multidimensional general grids

We present a new method for complex frequency estimation in several variables, extending the classical (1d) ESPRIT-algorithm. We also consider how to work with data sampled on non-standard domains (i.e going beyond multi-rectangles)

Economic Freedom and Growth:Decomposing the Effects

Most studies of the relation between economic freedom and growth of GDP have found a positive relation. One problem in this area is the choice of economic freedom measure. A single measure does notreflect the complex economic environment and a highly aggregated index makes it difficult to draw policy conclusions. In this paper we investigate what specific types of economic freedom measures that are important for growth. The robustness of the results is carefully analysed since the potential problem with multicollinearity is one of the negative effects of decomposing an index. The results show that economic freedom does matter for growth. This does not mean that increasing economic freedom, definedin general terms, is good for economic growth since some of the categories in the index are insignificant and some of the significant variables have negative effects.Economic growth; Economic freedom

Fast algorithms and efficient GPU implementations for the Radon transform and the back-projection operator represented as convolution operators

The Radon transform and its adjoint, the back-projection operator, can both be expressed as convolutions in log-polar coordinates. Hence, fast algorithms for the application of the operators can be constructed by using FFT, if data is resampled at log-polar coordinates. Radon data is typically measured on an equally spaced grid in polar coordinates, and reconstructions are represented (as images) in Cartesian coordinates. Therefore, in addition to FFT, several steps of interpolation have to be conducted in order to apply the Radon transform and the back-projection operator by means of convolutions. Both the interpolation and the FFT operations can be efficiently implemented on Graphical Processor Units (GPUs). For the interpolation, it is possible to make use of the fact that linear interpolation is hard-wired on GPUs, meaning that it has the same computational cost as direct memory access. Cubic order interpolation schemes can be constructed by combining linear interpolation steps which provides important computation speedup. We provide details about how the Radon transform and the back-projection can be implemented efficiently as convolution operators on GPUs. For large data sizes, speedups of about 10 times are obtained in relation to the computational times of other software packages based on GPU implementations of the Radon transform and the back-projection operator. Moreover, speedups of more than a 1000 times are obtained against the CPU-implementations provided in the MATLAB image processing toolbox

International Experience and the Performance of Scandinavian Firms in China

Western firms locating in China face a business environment that differs from their home country environment. The differences increase uncertainties and are negative for economic performance. However, firms may differ in their ability to overcome the difficulties, depending on their previous experience. In particular, firms with experience from regions similar to China might do comparably well. We conduct a survey of Scandinavian firms with subsidiaries in China to examine their economic performance. Our results show that subsidiaries in China perform better if the firms have subsidiaries in Hong Kong, Taiwan, or Singapore. In addition, the length of subsidiaries’ operation in China, and the experience from foreign countries outside of Greater China, are also positively affecting the subsidiaries’ economic performance.FDI; Firms; Experience; China; Scandinavia

Dealing with ignored attributes in choice experiments on valuation of Sweden's environmental quality objectives

Using a choice experiment, this paper investigates how Swedish citizens value three environmental quality objectives. In addition, a follow-up question is used to investigate whether respondents ignored any attributes when responding. The resulting information is used in the model estimation by restricting the individual parameters for the ignored attributes to zero. When taking the shares of respondents who considered both the environmental and the cost attributes (52-69 percent of the respondents) into account, then the WTPs for each attribute change if the respondents who ignored the attributes have a zero WTP. At the same time, we find evidence that not all respondents who claimed to have ignored an attribute really did. However, the most commonly ignored non-monetary attributes always have the lowest rankings in terms of WTP across all three environmental objectives. Thus, our results show that instead of ignoring, respondents seem to put less weight on the attributes they claimed to have ignored.Choice experiment, environmental quality objectives, follow-up question,

Measuring marginal values of noise disturbance from air traffic: Does the time of the day matter?

This paper analyzes the marginal willingness to pay for changes in noise levels related to changes in the volume of flight movements at a city airport in Stockholm, Sweden,by using a choice experiment. When estimating marginal willingness to pay for different times of the day and days of the week, we find that these vary with the temporal dimensions: mornings and evenings have higher marginal values. Interestingly, a substantial proportion of the respondents prefer no changes in the current noise level. The paper concludes with a policy discussion related to incentivebased pricing.Choice experiment; discrete choice; noise; airport

The Effect of Power Outages and Cheap Talk on Willingness to Pay to Reduce Outages

Using an open-ended contingent valuation survey, we analyze how (i) experience of a power outage due to one of the worst storms ever to hit Sweden and (ii) a cheap talk script affect respondents' WTP to avoid power outages. Experience significantly increases and a cheap talk script decreases the proportion of respondents with zero WTP. There is no significant effect in either case on stated WTP conditional on a positive WTP. The paper concludes with a discussion on the use of valuation studies shortly after the occurrence of an undesirable event.contingent valuation, cheap talk, experience, power outages

Non-Convex Rank/Sparsity Regularization and Local Minima

This paper considers the problem of recovering either a low rank matrix or a sparse vector from observations of linear combinations of the vector or matrix elements. Recent methods replace the non-convex regularization with $\ell_1$ or nuclear norm relaxations. It is well known that this approach can be guaranteed to recover a near optimal solutions if a so called restricted isometry property (RIP) holds. On the other hand it is also known to perform soft thresholding which results in a shrinking bias which can degrade the solution. In this paper we study an alternative non-convex regularization term. This formulation does not penalize elements that are larger than a certain threshold making it much less prone to small solutions. Our main theoretical results show that if a RIP holds then the stationary points are often well separated, in the sense that their differences must be of high cardinality/rank. Thus, with a suitable initial solution the approach is unlikely to fall into a bad local minima. Our numerical tests show that the approach is likely to converge to a better solution than standard $\ell_1$/nuclear-norm relaxation even when starting from trivial initializations. In many cases our results can also be used to verify global optimality of our method