预防液化石油气储罐应力腐蚀的初探

液化石油气储罐在工业和人民生活中有着广泛的应用,探讨液化石油气中所含H2S腐蚀介质对储罐的应力腐蚀及预防措施显得非常重要。     

General‐to‐Specific Model Selection Procedures for Structural Vector Autoregressions*

Structural vector autoregressive (SVAR) models have emerged as a dominant research strategy in empirical macroeconomics, but suffer from the large number of parameters employed and the resulting estimation uncertainty associated with their impulse responses. In this paper, we propose general‐to‐specific (Gets) model selection procedures to overcome these limitations. It is shown that single‐equation procedures are generally efficient for the reduction of recursive SVAR models. The small‐sample properties of the proposed reduction procedure (as implemented using PcGets) are evaluated in a realistic Monte Carlo experiment. The impulse responses generated by the selected SVAR are found to be more precise and accurate than those of the unrestricted VAR. The proposed reduction strategy is then applied to the US monetary system considered by Christiano, Eichenbaum and Evans (Review of Economics and Statistics, Vol. 78, pp. 16–34, 1996) . The results are consistent with the Monte Carlo and question the validity of the impulse responses generated by the full system.     

Hard Times or Great Expectations? Dividend Omissions and Dividend Cuts by UK Firms*

This paper uncovers an increasing proportion of quoted UK companies omitting cash dividends. Using a large panel of quoted UK firms, we estimate panel data probit models for the incidence of dividend omissions and cuts as functions of financial characteristics including cash flow, leverage, investment opportunities, investment and company size. These variables account for most of the increase in omission since 1995. There is relatively little evidence to link this to the major tax reform of 1997 that abolished tax refunds on dividend income payable to tax‐exempt institutions. Significant persistence effects indicate companies are slow to adjust their balance sheets through their dividend.     

Are stationarity and cointegration restrictions really necessary for the intertemporal budget constraint?

Time series related to fiscal and external deficits are commonly subjected to stationarity and cointegration tests to assess if the deficits are sustainable. Such tests are incapable of rejecting sustainability. The intertemporal budget constraint proves to be satisfied if either the debt series or the revenue and with-interest spending series are integrated of arbitrarily high order, i.e., stationary after differencing arbitrarily often. Revenues and spending do not have to be cointegrated. Rejections of low-order difference-stationarity and of cointegration are thus consistent with the intertemporal budget constraint. Error-correction-type policy reaction functions are suggested as more promising for understanding deficit problems.     

MEASURING THE OPERATIONAL EFFICIENCY OF COMMERCIAL BANKS IN NAMIBIA

This paper examines the efficiency of commercial banks in Namibia using the standard econometric frontier approach. Although two aspects of efficiency (scale and scope) receive our attention, the emphasis is on the latter which pertains to whether a firm produces as efficiently as it possibly can, given its size. Our results indicate that substantial economies of scale exist in commercial banking in Namibia. This will tend to suggest that commercial banks in Namibia can increase their efficiency by increasing their current scale of operation. The results for scope economies show that the current level of input combination does not make for maximum efficiency as sufficient scope exists for a more efficient combination of inputs. We believe this will reduce operating costs in the industry and stimulate efficiency.     

Intertemporal substitution and the liquidity effect in a sticky price model

The liquidity effect, defined as a decrease in nominal interest rates in response to a monetary expansion, is a major stylized fact of the business cycle. This paper first confirms that, with separable preferences, a low degree of intertemporal substitution in consumption is a necessary condition for the existence of the liquidity effect. In contrast to this result, in a model with non-separable preferences and capital accumulation it takes an implausibly high elasticity of intertemporal substitution to produce a liquidity effect. The robustness of these results to alternative degrees of nominal rigidities, capital adjustment costs and stochastic monetary processes is also analysed. We conclude that price stickiness, by itself, does not guarantee the existence of a liquidity effect.     

Interest rate corridors and reserves

This paper evaluates reserves regimes versus interest rate corridors, which have become competing frameworks for monetary policy implementation. Rate corridors, relying on lending and deposit facilities to create ceilings and floors for overnight interest rates, evince mixed results on controlling volatility. Reserve requirements allow period-average smoothing of interest rates but, even if remunerated, are subject to reserve avoidance activities. A system of voluntary, period-average reserve commitments could offer equivalent rate-smoothing advantages. If central banks created symmetric opportunity costs of meeting or falling short of period-average reserve requirements (or commitments), they could achieve flat reserve demand on settlement day.     

The future of social security

We analyze the effect of the projected demographic transition on the political support for social security, and equilibrium outcomes. Embedding a probabilistic-voting setup of electoral competition in the standard OLG model with capital accumulation, we find that intergenerational transfers arise in the absence of altruism, commitment, or trigger strategies. Closed-form solutions predict population ageing to lead to higher social security tax rates, a rising share of pensions in GDP, but eventually lower social security benefits per retiree. The response of equilibrium tax rates to demographic shocks reduces old-age consumption risk. Calibrated to match features of the U.S. economy, the model suggests that, in response to the projected demographic transition, social security tax rates will gradually increase to 16%. Other policies that distort labor supply will become less important; labor supply therefore will rise, in contrast with frequently voiced fears.     

Some Evidence on the Adjustment of Producer Prices*

We document producer price adjustment using a low‐inflation micro price dataset. On average 24% of prices adjust each month, with an average increase/decrease of 6%. Producer prices adjust more frequently than consumer prices, but their size of adjustment is typically smaller. Sectoral heterogeneity in the frequency of price adjustment is strongly related to heterogeneity in the cost structure. Fluctuations in aggregate producer price inflation occur to a large extent through variation in the relative share of upward and downward price adjustment.     

THE CHANGING VOLATILITY OF THE SOUTH AFRICAN ECONOMY

During the last decade economic literature explored the presence of and reasons for what became known as “the great moderation” in the US and other G7 countries. “The great moderation” describes the decrease in economic volatility experienced in many of the G7 countries. This paper finds that in South Africa volatility is also not constant (it even finds that there are autoregressive conditional heteroskedastic effects present) and that volatility also decreased, particularly since 1994. Following the literature, the paper explores several reasons for this decrease and finds that smaller shocks, better monetary policy and improvements in the financial sector that place less liquidity constraints on individuals and allow them to manage their debt better are some of the main reasons for the reduction in the volatility of the South African economy. The literature on the G7 also suggests that better inventory management contributed to the lower volatility. However, this seems not to be true for South Africa.