Saddlepoint approximations to the mean and variance of the extended hypergeometric distribution

Conditional inference on 2 x 2 tables with fixed margins and unequal probabilities is based on the extended hypergeometric distribution. If the support of the distribution is large, exact calculation of the conditional mean and variance of the table entry may be computationally demanding. This paper proposes a single‐saddlepoint approximation to the mean and variance. While the approximation achieves acceptable accuracy for ordinary practical purposes, an alternative saddlepoint approximation is provided that gives much closer to exact results. It improves the accuracy of current approximations to up to more than four powers of ten.     

Economies in Transition: How Important Is Trade Openness for Growth?*

We investigate the effect of trade openness on economic growth in transition countries using a transparent statistical methodology that leads to data‐driven case studies. In particular, we employ synthetic control methods in a panel of transition economies and compare GDP growth in treated (that is, open) countries with growth in a convex combination of similar but untreated (that is, closed) countries. We find that trade liberalization tends to have a positive effect on the pattern of real GDP per capita. One of our most robust results shows that making the transition without opening up to trade considerably hampers growth.     

天津市武清区大气O_3、NO_2和CO浓度变化特征研究

文章利用2014年天津市武清区大气污染物臭氧(O_3)、二氧化氮(NO_2)和一氧化碳(CO)的监测数据,分析研究武清区O_3及其前体物NO_2和CO等大气污染物浓度水平和变化特征。结果表明武清区O_3浓度水平呈现明显的季节变化特征。夏季O_3浓度为106μg·m~(-3),冬季浓度为28μg·m~(-3),主要与光化学反应在夏季比较强烈,冬季紫外强度和平均温度均较低,光化学反应较弱有关。2014年武清区大气中NO_2年均值为51μg·m~(-3),CO年均值为1.9 mg·m~(-3),冬季是NO_2和CO浓度最高的季节。     

Capital Controls,Global Liquidity Traps,and the International Policy Trilemma*

The zero bound on interest rates introduces a new dimension to the trilemma in international policy. The openness of the international financial market might render monetary policy ineffective, even within a system of fully flexible exchange rates, because shocks that lead to a liquidity trap in one country are propagated through financial markets to other countries. However, the effectiveness of monetary policy can be restored by the imposition of capital controls. We derive the optimal response of monetary policy to a global liquidity trap in the presence of capital controls. We show that, even though capital controls might facilitate effective monetary policy, capital controls are not generally desirable in terms of welfare.     

Does Human Capital Protect Workers against Exogenous Shocks? Evidence from Panel Data on South Africa during the 2008‐2009 Crisis

The financial and economic crisis of 2008 and 2009 took a heavy toll on the South African economy. The economy contracted for the first time since 1998 and entered recession during the fourth quarter of 2008. The gross domestic product contraction was soon transmitted to the labour market. Between the second quarters of 2008 and 2009, employment fell by 3.8%. However, not all individuals were hit with the same intensity. Using panel data from a quarterly labour force survey unique in the African context, we find that human capital (i.e. education as years of schooling and workforce experience) provided a buffer against the shock. After controlling for observable characteristics, education and experience showed the potential to entirely offset the effect of the recession on the likelihood of employment. This has important policy implications, as it strengthens the case for strategic investments in human capital and helps identify the unskilled as having the greatest need for social safety net interventions during a recession.     

MODELLING A REGIME‐SHIFTING BEVERIDGE CURVE

This paper offers new insights into Beveridge curve analysis by modelling the unemployment–vacancy rate relationship within a Markov regime‐switching environment in which the probabilities of curve‐shifting are determined endogenously by shift factors. Shift factors include structural factors such as labour market participation and net migration, while cyclical variables include GDP growth, the real rate of interest, and labour productivity. This approach enables us to estimate regime‐specific parameters and to assess the role played by these factors in influencing the transition probabilities of switching between regimes. Using New Zealand data, we show that increases in the participation rate have shifted the Beveridge curve inward, while increases in net migration have shifted the curve outward.     

Pure jump models for pricing and hedging VIX derivatives

Recent non-parametric statistical analysis of high-frequency VIX data (Todorov and Tauchen, 2011) reveals that VIX dynamics is a pure jump semimartingale with infinite jump activity and infinite variation. To our best knowledge, existing models in the literature for pricing and hedging VIX derivatives do not have these features. This paper fills this gap by developing a novel class of parsimonious pure jump models with such features for VIX based on the additive time change technique proposed in Li et al., 2016a, Li et al., 2016b. We time change the 3/2 diffusion by a class of additive subordinators with infinite activity, yielding pure jump Markov semimartingales with infinite activity and infinite variation. These processes have time and state dependent jumps that are mean reverting and are able to capture stylized features of VIX. Our models take the initial term structure of VIX futures as input and are analytically tractable for pricing VIX futures and European options via eigenfunction expansions. Through calibration exercises, we show that our model is able to achieve excellent fit for the VIX implied volatility surface which typically exhibits very steep skews. Comparison to two other models in terms of calibration reveals that our model performs better both in-sample and out-of-sample. We explain the ability of our model to fit the volatility surface by evaluating the matching of moments implied from market VIX option prices. To hedge VIX options, we develop a dynamic strategy which minimizes instantaneous jump risk at each rebalancing time while controlling transaction cost. Its effectiveness is demonstrated through a simulation study on hedging Bermudan style VIX options.     

Evaluation of the long-term cost-effectiveness of IDegLira versus liraglutide added to basal insulin for patients with type 2 diabetes failing to achieve glycemic control on basal insulin in the USA

Background and aims: IDegLira, a fixed ratio combination of insulin degludec and glucagon-like peptide-1 receptor agonist liraglutide, utilizes the complementary mechanisms of action of these two agents to improve glycemic control with low risk of hypoglycemia and avoidance of weight gain. The aim of the present analysis was to assess the long-term cost-effectiveness of IDegLira vs liraglutide added to basal insulin, for patients with type 2 diabetes not achieving glycemic control on basal insulin in the US setting.

Methods: Projections of lifetime costs and clinical outcomes were made using the IMS CORE Diabetes Model. Treatment effect data for patients receiving IDegLira and liraglutide added to basal insulin were modeled based on the outcomes of a published indirect comparison, as no head-to-head clinical trial data is currently available. Costs were accounted in 2015?US dollars ($) from a healthcare payer perspective.

Results: IDegLira was associated with small improvements in quality-adjusted life expectancy compared with liraglutide added to basal insulin (8.94 vs 8.91 discounted quality-adjusted life years [QALYs]). The key driver of improved clinical outcomes was the greater reduction in glycated hemoglobin associated with IDegLira. IDegLira was associated with mean costs savings of $17,687 over patient lifetimes vs liraglutide added to basal insulin, resulting from lower treatment costs and cost savings as a result of complications avoided.

Conclusions: The present long-term modeling analysis found that IDegLira was dominant vs liraglutide added to basal insulin for patients with type 2 diabetes failing to achieve glycemic control on basal insulin in the US, improving clinical outcomes and reducing direct costs.     

Remittance,Institutions and Investment Volatility Interactions: An Intercontinental Analysis

Generating massive investment for growth and development has been one of the main policy goals of most economies around the globe. Countries, most especially developing ones, are highly susceptible to investment volatility owing largely to the fragile nature of their economies as well as weaknesses in terms of dysfunctional institutions. Therefore, sound economic management suggests the need to better understand possible sources for mitigating the adverse effects of investment volatility. Remittances have been identified as important capital flows which do a good job of dousing macroeconomic volatilities. It is on this basis that the study sought to uncover the causal relationship between remittances and investment volatility via the intermediating role of institutions. Using a panel of 70 countries and the system Generalized Method of Moments (GMM) estimator, three insightful outcomes come to the fore. First, remittances played countercyclical roles across the estimated regressions. Second, institutional quality had no significant role in mitigating investment volatility and lastly, the interactive terms of both remittances and institutions significantly mitigated the negative impacts of investment volatility with the exception of the political component of the institutional architecture. Policy suggestions are drawn based on our results.     

The importance of firing costs and the Hosios condition in search models with endogenous job destruction

We construct a DSGE search model with endogenous job destruction, incorporating wage rigidities, firing costs and unemployment benefit. We investigate the most important factors in matching the model’s cyclical properties with empirical data, particularly those of job creation rates (JCR) and job destruction rates (JDR). Firing costs assist significantly in explaining the procyclicality of JCR, the negative correlation of JCR and JDR, and the persistence of vacancies. They also decrease the counter-cyclicality of job turnover. We also postulate that the Hosios condition helps explain the negative correlation of JCR and JDR and vacancies’ persistence. Varying wage rigidities and unemployment income, however, do not improve the results.