Social Security and personal saving: 1971 and beyond

Feldstein (1996, 1974) reported that Social Security in the U.S.A. reduced personal saving (“saving”) in 1992 (1971) by $416 ($61) billion. I reestimate his life-cycle consumption specification using data from the latest NIPA revision, correct his calculations, and find that the implied reduction in 1992 (1971) saving is now $280 ($22) billion, 48% (16%) of actual net private saving, with a standard error of $114 ($14) billion. If structural breaks around WWII and the 1972 Social Security amendments (which raised real per capita SSW by 22%) are allowed, and the market value of Treasury debt included in the specification, the reduction in 1971 and 1992 saving attributable to Social Security is at most 0.55 times its standard error, and 12% of net private saving. I then reestimate the preferred specification of Coates and Humphreys (1999), allowing for these structural breaks and relaxing other restrictions. The implied effect of Social Security on saving is again statistically zero. First version received: September 2000/Final version received: September 2001 RID="*" ID="*"  I thank Les Oxley for pointing out that correcting for AR(1) residuals is not a categorical imperative but a cultural relative, in which case common factor restrictions are crucial.     

Information reduction via level crossings in a credit risk model

This paper provides an alternative credit risk model based on information reduction where the market only observes the firm’s asset value when it crosses certain levels, interpreted as changes significant enough for the firm’s management to make a public announcement. For a class of diffusion processes we are able to provide explicit expressions for the firm’s default intensity process and its zero-coupon bond prices.      

Life cycle assessment in the food supply chain: a case study

This research aims at assessing the environmental impact of the poultry supply chain from cradle to grave using case study research and also life cycle assessment (LCA). While a limited number of generic poultry production LCA studies have been published, fewer yet assess the whole process of a specific organisation, none comparing the increased impact of further processing. Our results show that irrespectively of the impact assessment method utilised, the process of producing portions is considerably higher in total environmental impact due to the extra raw material required to produce the same mass into retail. Our research contributes to the growing number of LCA studies and could be used by practitioners for comparison against national and international averages. From a theoretical point of view, this research provides new insights into the relationship between vertically integrated supply chains and environmental performance which has not been examined in the past.     

Estimating Transition Probabilities from a Time Series of Independent Cross Sections

This paper considers the implementation of a nonstationary, heterogeneous Markov model for the analysis of a binary dependent variable in a time series of independent cross sections. The model, previously considered by M offitt (1993), offers the opportunity to estimate entry and exit transition probabilities and to examine the effects of time-constant and time-varying covariates on the hazards. We show how ML estimates of the parameters can be obtained by Fisher's method-of-scoring and how to estimate both fixed and time-varying covariate effects. The model is exemplified with an analysis of the labor force participation decision of Dutch women using data from the Socio-economic Panel (SEP) study conducted in the Netherlands between 1986 and 1995. We treat the panel data as independent cross sections and compare the employment status sequences predicted by the model with the observed sequences in the panel. Some open problems concerning the application of the model are also discussed.     

Research returns redux: a meta-analysis of the returns to agricultural R&D

A total of 289 studies of returns to agricultural R&D were compiled and these provide 1821 estimates of rates of return. After removing statistical outliers and incomplete observations, across the remaining 1128 observations the estimated annual rates of return averaged 65 per cent overall — 80 per cent for research only, 80 per cent for extension only, and 47 per cent for research and extension combined. These averages reveal little meaningful information from a large body of literature, which provides rate-of-return estimates that are often not directly comparable. This study was aimed at trying to account for the differences. Several features of the methods used by research evaluators matter, in particular assumptions about lag lengths and the nature of the research-induced supply shift.