AGGREGATE STABILITY AND WATER RETENTION NEAR SATURATION CHARACTERISTICS AS AFFECTED BY SOIL TEXTURE, AGGREGATE SIZE AND POLYACRYLAMIDE APPLICATION

Understanding the effects of soil intrinsic properties and extrinsic conditions on aggregate stability is essential for the development of effective soil and water conservation practices. Our objective was to evaluate the combined role of soil texture, aggregate size and application of a stabilizing agent on aggregate and structure stability indices (composite structure index [SI], the and n parameters of the VG model and the S-index) by employing the high energy (0-5.0 J kg(-1)) moisture characteristic (HEMC) method. We used aggregates of three sizes (0.25-0.5, 0.5-1.0 and 1.0-2.0 mm) from four semi-arid soils treated with polyacrylamide (PAM). An increase in SI was associated with the increase in clay content, aggregate size and PAM application. The value of increased with the increase in aggregate size and with PAM application but was not affected by soil texture. For each aggregate size, a unique exponential type relationship existed between SI and . The value of n and the S-index tended, generally, to decrease with the increase in PAM application; however, an increase in aggregate size had an inconsistent effect on these two indices. The relationship between SI and n or the S-index could not be generalized. Our results suggest that (i) the effects of PAM on aggregate stability are not trivial, and its application as a soil conservation tool should consider field soil condition, and (ii), n and S-index cannot replace the SI as a solid measure for aggregate stability and soil structure firmness when assessing soil conservation practices

Using factor analysis to distinguish between effective and ineffective aggregate stability indices

Several existing aggregate stability indices are commonly used to represent aggregate stability of soil. Consequently, there is a need to determine how well these common indices characterize or represent aggregate stability. The main objective of this study was to use a multivariate statistical method called factor analysis to determine the effectiveness of eight common indices in measuring aggregate stability. Eighty soil samples (Oxisols and Ultisols) were taken from soil depth of 0-150 mm and from different land uses, such as oil palm, coffee, tea, rubber, pine, fallow, vegetables, and grassland. Aggregate stability of these soils were determined by wet-sieving and water dispersion of the primary particles. Eight aggregate stability indices were used: AIA (average fraction of intact aggregates), WSA >0.3 and >0.5 (water-stable aggregates larger than size 0.3 and 0.5 mm, respectively), MWD (mean weight diameter), CR (clay ratio), WDC (water-dispersible clay), WDCS (water-dispersible clay plus silt), and TP (turbidity percentage). The factor analysis showed that all the aggregate stability indices were related to two common factors, namely, aggregate breakdown resistance and dispersion. By determining how well an aggregate stability index is correlated to either one or both these common factors, the factor analysis ranked the effectiveness of the indices as follows: WSA >0.3 = WDCS > AIA > MWD > WDC > CR. Due to the fact that WSA >0.5 is correlated very strongly with WSA >0.3, both the indices ought to be as effective as the other. The TP index, however, had a questionable efficacy as an aggregate stability index. Based on the findings of this study, it was therefore concluded that only two indices, WSA >0.3 (or WSA >0.5) and WDCS, were sufficient to represent the whole soil aggregate stability

Soil Aggregate Stability: Its Evaluation and Relation to Organic Matter Constituents and Other Soil Properties

The purpose of this study were: 1) to compare the aggregate stability of individual aggregate size fractions, 2) to determine the interrelationship and efficiency of several aggregate stability indices, and 3) to determine the relationship and importance of organic matter and other soil constituents on aggregate stability. To compare the aggregate stability of individual aggregate size fractions, a mathematical model was developed to estimate the breakdown of individual aggregate size fractions in the wet-sieving (using nested sieves) method. This model was validated and calibrated by comparing the estimation values to the actual aggregate breakdown values by paired sample t-test, linear regression and prediction error sum of squares. The average percentage of stable aggregates for all aggregate size fractions were represented in an index called average intact aggregates (AlA). Factor analysis was used to determine the interrelationship and efficiency of several aggregate stability indices. Aggregate stability of eight soil samples were measured with eight indices: percentage of water-stable aggregates >0.3 mm (WSA >0.3) and >0.5 mm (WSA >0.5), AlA, water-dispersible clay (WDC), waterdispersible clay and silt (WDCS), mean weight diameter after wet-sieving (MWDw), turbidity percentage (TP), and clay ratio (CR)

Econometric modelling for short-term inflation forecasting in the EMU.

Inflation forecasts are in great demand by agents in financial markets and monetary authorities that also require frequent updates. In the case of the EMU, these can be done monthly using Harmonised Indices of Consumer Prices (HICP). Analysing the HICP it was detected in a previous paper that breaking down the HICP in a vector of n sectors so that each price index component corresponds to a group of relatively homogeneous markets, or in a vector of n countries, there are in both cases fewer than (n-1) cointegration relationships. It can then be said that the components of the index are not fully cointegrated in the sense that there is more than one common trend in the HICP vector. In such a case, one way to increase sample information about the HICP trend is to consider the n price components and approach disaggregated econometric modelling. The paper shows that the breakdown that joins both criteria by considering a price index for each large group of markets in each country improves EMU inflation forecasts and establishes a framework in which general and specific explanatory variables and non-linear structures can be introduced for further improvements. The paper shows that VEqCM of ten price indices " two sectors by five geographical areas " including three cointegration relationships, with a sector-block diagonal restriction, generates forecasts of the year-on-year inflation rate in the HICP such that their error variances are one third or one fifth of the forecast errors from an aggregate ARIMA model, depending whether the horizon is three or twelve months. This vector model also provides better forecasts than single-equation models or alternative vector models for the components. A successful formulation of the vector model requires the inclusion of dummy variables to take account of special events such as seasonality changes due to sales, the introduction of the euro, Greece becoming a member of the EMU, the introduction of ecological taxes, bad weather periods and others events altering the evolution of unprocessed food prices, etc. and the inclusion of international Brent prices in euros. With the breakdown used in the paper it is shown that a usual measure of core inflation is not a good predictor of total inflation, but the interest in core inflation could lie in the fact that its corresponding price index is constructed with price indices in which innovations are more persistent than those in the other consumer price indexes excluded from the core. The disaggregated forecasts presented in this paper are useful for policy-making because they tell us which sectors have the highest expected inflation rates and how persistent are the shocks affecting different sectors

On the European readiness for flexicurity: Empirical evidence with OECD/HBS methodologies and reform proposals

The Fourth European Working Conditions Survey (European Foundation 2007) is used to investigate the readiness of Europe to flexicurity labour market reforms proposed by the European Commission (= flexibilization of employment relations compensated by improvements in employment security backed up by lifelong learning). For this purpose, composite indicators of flexibility, precariousness and decentness of work are constructed with the OECD and HBS (Hans Boeckler Stiftung) methodologies which differ in scaling. Then the indices are visualized with specially designed tabular graphs and analysed. Both methodologies give quite similar results. It is revealed that (1) factual flexibility (as it is practiced) radically differs from institutional flexibility (prescribed by employment protection legislation), (2) flexibility and precariousness of work correlate with statistical certainty, moreover, no country combines high flexibility and low precariousness; (3) flexibilization has the strongest negative effect on employability; (4) there is an acute shortage of learning options, (5) learning makes a negative impact on job satisfaction, at the same time job stability is top esteemed, but not income which is ranked only 6th, and (6) working conditions of flexibly employed is worse than of normally employed, being even below the European average. It implies that the Commission's conception of flexicurity, neglecting the socio-economic reality, can be hardly efficient and successful. Therefore, an alternative implementation of flexicurity is proposed in the form of flexinsurance which assumes that the employer's contribution to social security should be proportional to the flexibility (precariousness) of the employment contract. To stimulate employers to equalize working conditions of normal and atypical employees, it is proposed to introduce a workplace tax for bad working conditions which should protect 'the working environment' in the same way as the green tax protects the natural environment. --

Credit growth in Central and Eastern Europe: convergence or boom?

Credit to the private sector has been growing very rapidly in a number of Central and Eastern European countries in recent years. The main question is whether this dynamics is an equilibrium convergence process or may rather pose stability risks. Using panel econometric techniques, this paper attempts to identify the equilibrium credit/GDP levels of the new EU countries, disentangling the observed growth into an equilibrium trend and an excess (boom) component. In the paper the pooled mean group estimator was used for its flexibility and efficiency. Using instrumental variable technique we tested whether long run endogeneity affects the consistency. The estimations show that large part of the credit growth in new member states can be explained by the catching-up process, and, in general, credit/GDP ratios are below the levels consistent with macroeconomic fundamentals. However, in Latvia and Estonia credit growth is found to be significantly faster than what would be justified along the equilibrium path

Cloud Index Tracking: Enabling Predictable Costs in Cloud Spot Markets

Cloud spot markets rent VMs for a variable price that is typically much lower than the price of on-demand VMs, which makes them attractive for a wide range of large-scale applications. However, applications that run on spot VMs suffer from cost uncertainty, since spot prices fluctuate, in part, based on supply, demand, or both. The difficulty in predicting spot prices affects users and applications: the former cannot effectively plan their IT expenditures, while the latter cannot infer the availability and performance of spot VMs, which are a function of their variable price. To address the problem, we use properties of cloud infrastructure and workloads to show that prices become more stable and predictable as they are aggregated together. We leverage this observation to define an aggregate index price for spot VMs that serves as a reference for what users should expect to pay. We show that, even when the spot prices for individual VMs are volatile, the index price remains stable and predictable. We then introduce cloud index tracking: a migration policy that tracks the index price to ensure applications running on spot VMs incur a predictable cost by migrating to a new spot VM if the current VM's price significantly deviates from the index price.Comment: ACM Symposium on Cloud Computing 201

Primary commodity prices and macroeconomic variables : a long run relationship

In recent years, fluctuations in such macroeconomic variables as interest rates and exchange rates appear to have significantly affected primary commodity prices. This paper studies the relationship between commodity prices and various macroeconomic variables. It focuses particularly on interest rates because of the important role they play in the portfolio adjustment model, in which investors move between commodities, bonds and money as interest rates change. The paper concludes that there is a long run quantifiable relationship between real interest rates and real commodity prices, but not between real commodity prices and either consumer prices or the money supply. Commodity prices in nominal terms strongly affect consumer prices but not the reverse - and some groups of commodity prices can be reliable indicators of movements in consumerprices. Changes in the money supply affect commodity prices, but not the reverse, and the relationship is not quantifiable.Insurance&Risk Mitigation,Economic Theory&Research,Markets and Market Access,Access to Markets,Environmental Economics&Policies

Monitoring hedge funds: a fi nancial stability perspective.

Investor inflows into hedge funds have been significant in recent years and they have continued unabated. As a result, the presence and role of these investment funds in global capital markets have become increasingly important, and to a much greater extent than the amount of capital they manage would suggest. This is because hedge funds can, and often do, leverage their investment positions. Indeed, their leveraged assets are sometimes comparable with the assets of large banks. The growing and active participation of hedge funds in a large number of financial markets implies that the functioning of these markets could be seriously affected if the hedge fund sector came under stress. The positive contribution of hedge funds to the efficiency and liquidity of global financial markets is widely recognised, but there are also concerns that in times of stress their activities may create risks to financial stability. The lack of transparency and limited publicly available information about their balance sheets and activities poses significant challenges for financial stability analysis. While it is possible to base such an analysis on a multitude of information sources on hedge fund activities – including dedicated financial media, commercial hedge fund databases, quarterly industry reports, hedge fund return indices, academic studies, some supervisory data and market surveillance – these sources are not sufficient for an adequate monitoring and robust evaluation of hedge fund activities from a financial stability perspective. Three groups of indicators could be important for financial stability analysis, namely those which shed light on banks’ exposures to hedge funds, provide yardsticks of the crowding of hedge fund trades, and facilitate the gauging of endogenous hedge fund vulnerabilities. The latter group would include the measures of funding liquidity risk, leverage and exposures to market risk factors. The construction of all these indicators would be greatly facilitated if basic information on hedge fund balance sheets were available. Since this is not the case, various indirect estimation methods have to be relied upon. A “desirable vs. available” analysis reveals the most important information gaps, but it does not aim at providing recommendations on how to enhance hedge fund transparency in practice. Instead, it proposes three elements which a transparency framework would ideally include: fi rst, more aggregate information to all market participants; second, a highly standardised reporting template that would make disclosures more effective; fi nally, adequate information for a joint analysis of the aggregate activities of banks, hedge funds and other highly leveraged institutions in order to have a comprehensive picture of risks to the smooth functioning of financial markets.

The role of the wealth distribution on output volatility

We explore the link between wealth inequality and business cycle fluctuations in a two-sector neoclassical growth model with endogenous labor and heterogeneous agents. Assuming that wealth inequality is described by the distribution of shares of capital, we show that in the most plausible situations wealth equality is a stabilizing factor. In particular, when wealth is Pareto distributed and preferences generate non linear absolute risk tolerance indices, a rise in the Gini index may only be associated to a rise in volatility.When individual preferences are such that the individual absolute risk tolerance indices are linear, as with HARA utility, even a low level of taste heterogeneity ensures that a rise in inequality may not reduce volatility, and this independently of the wealth distribution.Finally, we note that such a clear result is at odd with the existing related literature.Wealth Inequality, Pareto distribution, Gini index, Elastic Labor Supply, Macroeconomic Volatility, Endogenous Equilibrium Business Cycles.