Universal Voting Protocol Tweaks to Make Manipulation Hard

Voting is a general method for preference aggregation in multiagent settings, but seminal results have shown that all (nondictatorial) voting protocols are manipulable. One could try to avoid manipulation by using voting protocols where determining a beneficial manipulation is hard computationally. A number of recent papers study the complexity of manipulating existing protocols. This paper is the first work to take the next step of designing new protocols that are especially hard to manipulate. Rather than designing these new protocols from scratch, we instead show how to tweak existing protocols to make manipulation hard, while leaving much of the original nature of the protocol intact. The tweak studied consists of adding one elimination preround to the election. Surprisingly, this extremely simple and universal tweak makes typical protocols hard to manipulate! The protocols become NP-hard, #P-hard, or PSPACE-hard to manipulate, depending on whether the schedule of the preround is determined before the votes are collected, after the votes are collected, or the scheduling and the vote collecting are interleaved, respectively. We prove general sufficient conditions on the protocols for this tweak to introduce the hardness, and show that the most common voting protocols satisfy those conditions. These are the first results in voting settings where manipulation is in a higher complexity class than NP (presuming PSPACE $\neq$ NP)

Wealth Effects in Emerging Market Economies

We build a panel of 14 emerging economies to estimate the magnitude of housing, stock market, and money wealth effects on consumption. Using modern panel data econometric techniques and quarterly data for the period 1990/1-2008/2, we show that; (i) wealth effects are statistically significant and relatively large in magnitude; (ii) housing wealth effects tend to be smaller for Asian emerging markets while stock markets wealth effects are, in general, smaller for Latin American countries; (iii) housing wealth effects have increased for Asian countries in recent years; and (iv) consumption reacts stronger to negative than to positive shocks in housing and financial wealth.wealth effects, consumption, emerging markets.

Asset prices, Credit and Investment in Emerging Markets

We build a panel of 31 emerging economies to uncover the determinants of private investment growth in emerging markets. Using several econometric techniques and quarterly data for the period 1990:1-2008:3, we show that: (i) the GDP and the cost of capital are among the fundamental determinants of private investment; (ii) the equity price impacts positively and significantly on investment; (iii) financial factors (such as, credit and lending rate) play an important role on the dynamics of investment, in particular, for Asian and Latin American countries; (iv) investment growth exhibits substantial persistence and responds sluggishly to shocks; and (v) crises episodes magnify the negative response of investment.investment, credit, asset prices, emerging markets.

Mechanics of invagination and folding: Hybridized instabilities when one soft tissue grows on another.

We address the folding induced by differential growth in soft layered solids via an elementary model that consists of a soft growing neo-Hookean elastic layer adhered to a deep elastic substrate. As the layer-to-substrate modulus ratio is varied from above unity toward zero, we find a first transition from supercritical smooth folding followed by cusping of the valleys to direct subcritical cusped folding, then another to supercritical cusped folding. Beyond threshold, the high-amplitude fold spacing converges to about four layer thicknesses for many modulus ratios. In three dimensions, the instability gives rise to a wide variety of morphologies, including almost degenerate zigzag and triple-junction patterns that can coexist when the layer and substrate are of comparable softness. Our study unifies these results providing understanding for the complex and diverse fold morphologies found in biology, including the zigzag precursors to intestinal villi, and disordered zigzags and triple junctions in mammalian cortex.T. T. acknowledges the Academy of Finland for funding. The computational resources were provided by CSC – IT Center for Science. J.B. acknowledges the 1851 Royal Commission and Trinity Hall Cambridge for funding.This is the author accepted manuscript. The final version is available from APS via http://dx.doi.org/10.1103/PhysRevE.92.02272