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Essays in nonparametric econometrics with applications to the economics of productivity and innovation
No full textIl presente lavoro si propone di applicare metodi di avanguardia nella teoria econometrica
ed, in quest’ottica di rivisitare una serie di questioni economiche relative
ai temi della produttività, della tecnologia e dell’innovazione.
Il primo capitolo della tesi si concentra sul contesto parametrico. La letteratura
mainstream sull’econometria della produttività e sul cambiamento tecnologico (CT)
assumono l’additività del CT, introducendo cosı la neutralità à la Hicks derivante dal
CT all’interno del modello. In questa prospettiva, all’ interno del capitolo si stima una
funzione di produzione a livello di azienda che permette di allontanarsi dalla ipotesi
usuale di neutralità à la Hicks relativa al CT. In parallelo, il capitolo affronta il tema
dell’ endogenita dell’innovazione la quale è considerata una misura della CT. Le
specificazioni parametriche che consentono un cambiamento tecnico non Hicks-neutral
sono derivate. Il capitolo presenta anche delle condizioni verificabili per approssimazioni
parametriche comuni, in base alle quali vale la neutralità Hicks. Le specificazioni
Cobb-Douglas sono stimate adottando i metodi IV per un effetto eterogeneo dell’innovazione
sulla produttività. I risultati empirici rifiutano la neutralità à la Hicks rispetto
alla presenza di progresso tecnico capital-saving.
Il secondo capitolo è connesso ai temi espressi all’interno del primo in una pluralità
di aspetti. Il tema della localizzazione del cambiamento tecnologico viene affrontata
utilizzando la serie di dati sulle aziende del capitolo precedente. A tal proposito, al
fine di riconsiderare il rapporto tra innovazione e produttività, sono impiegati i recenti
progressi sulla regressione kernel strumentale generalizzata. Tale esercizio permette di
evidenziare l’eventuale presenza degli effetti di localizzazione di una variabile di innovazione
endogena e, grazie alla ”smoothing” delle variabili discrete, di tenere conto delle
tecnologie completamente eterogenee tra i diversi settori. Tali questioni sono estremamente
rilevanti sia da una prospettiva teorica sia in termini di policy implications, ma
non possono essere affrontate con l’adozione di approcci parametrici comuni. Il capitolo
affronta anche il tema delle prestazioni predittive degli stimatori non parametrici
rispetto ad alcune alternative parametriche. I risultati i) indicano che lo stimatore non
parametrico proposto produce risultati migliori di quelli parametrici e ii) evidenziano
alcuni modelli rilevanti che possono essere rilevati solo utilizzando lo stimatore non
parametrico.
Il terzo capitolo riesamina la questione delle ricadute internazionali delle attività di
ricerca e sviluppo utilizzando metodi non parametrici, e verifica la validità dei risultati
principali forniti nella letteratura rispetto alla possibile esistenza di non linearità,
effetti di soglia e di relazioni non additive. In quest’ottica, esso considera una stimasieve
di un modello di dati panel di diffusione tecnologica tra i paesi, focalizzandosi in
particolar modo sulla questione della dipendenza dell’errore sezione trasversale. L’approccio
semiparametrico adottato è un’estensione del modello fattore parametrico da
Pesaran (2006). Il confronto tra l’approccio parametrico e semiparametrico rivela una
prestazione migliore di quest’ultimo. Dal punto di vista economico, i risultati mostrano
nuove prove rispetto ai benefici dei programmi di ricerca e sviluppo nazionali ed
esteri per i paesi.
Infine, l’ultimo capitolo della tesi è una revisione della regressione kernel non parametrica.
Seguendo, soprattutto, il lavoro di Li e Racine (2007), riassume le caratteristiche
chiavi di ”least squares cross validation” e della regressione kernel usando
approcci costanti locali, lineari locali o polinomi locali.This thesis is concerned with applying frontier methods in econometric theory, to
revisit relevant economic questions concerning productivity, technology and innovation.
The focal point of this thesis is to try to employ econometric techniques that may allow
us to depart from the usual assumptions of linearity or additivity of the model, as is
usually found in economic literature. Therefore, a binding common ground of all the
chapters of this thesis is relaxing these restrictive assumptions, in economic topics
relevant to productivity and innovation, in micro and macro level. In this framework,
recent advancements in nonparametric econometric theory allow relaxing such model
restrictions.
The first chapter estimates a production function at firm level that allows departing
from the standard hypothesis of Hicks-neutral technical change. Simultaneously,
it is coping with the endogeneity of innovation, the latter being considered a measure
of TC. Parametric specifications that allow non-Hicks neutral technical change
are derived. The chapter also presents testable conditions, for common parametric
approximations, under which Hicks neutrality holds. Cobb-Douglas specifications are
estimated adopting IV methods for heterogeneous effect of innovation on productivity.
The empirical results reject Hicks neutrality towards the presence of a capital-saving
TC. Finally, this chapter serves as a link with the nonparametric approaches developed
in the following ones.
In the second chapter, the issue of localization of technical change is addressed
using the firm level dataset of the previous chapter. Recent advances on generalized
kernel instrumental regression are exploited in order to revisit the relationship between
innovation and productivity. This allows to highlight the possible presence of a localized
effect of an endogenous innovation variable and, thanks to smoothing discrete
variables, also to account for fully heterogeneous technologies across sectors. Such
issues are extremely relevant from both a theoretical and a policy oriented perspective
but cannot be addressed by adopting common parametric approaches. The issue of
the predictive performances of this nonparametric estimator when compared to some
parametric alternatives is also addressed. The results i) indicate that the proposed
nonparametric estimator performs better than parametric ones and ii) reveal some
relevant patterns that can only be detected using the nonparametric estimator.
The third chapter revisits the issue of international R&D spillovers by using nonparametric
methods, and tests the validity of the main results provided in the literature
with respect to the possible existence of nonlinearities, threshold effects and
non-additive relations. It considers a sieve estimation of a panel data model of technology
diffusion among countries, paying attention to the issue of error cross sectional
dependence. The adopted semiparametric approach is an extension of the parametric
factor model by Pesaran (2006). The comparison between the parametric and the
semiparametric approach reveals a better performance of the latter. From an economic
viewpoint, the results show new evidence with respect to the benefits of countries from domestic and foreign R&D.
Finally, the last chapter of the thesis is a review of the nonparametric kernel regression.
Following, mainly, the work of Li and Racine (2007), it summarizes the key
features of least squares cross validation and the kernel regression using local constant,
local linear or local polynomial approaches. Moreover, the nonparametric IV kernel
regression is presented, along with the relevant topics of ill-posed inverse problems
and regularization methods. This chapter serves also as an informal “appendix” of
the previous chapters, especially for the ones concerning kernel regression, because it
provides useful insights of the underlying methodologies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
In-hospital direct cost of acute stroke
No full textStroke is the first cause of disability and the third cause of death worldwide. Moreover, in the western countries, the stroke patients are the most frequent users of all the health services and the hospital budgets. At the same time, 10% of the Gross Domestic Product (GDP) is annually spent on health in relation with the average 8.9% of the Organisation for Economic Co-operation and Development (OECD) countries. Aim of this study is the economic evaluation on the in-hospital cost of patients with an acute stroke in Greece and the identification of potential independent factors influencing this cost. Demographic and clinical data were recorded on 429 consecutive patients with an acute stroke (ischemic and hemorrhagic), admitted to the University General Hospital of Patras during a period of 18 months. We calculated the cost, individually for each patient, from the stroke onset until the discharge from the hospital. The cost was measured in euro (€), according to the real expenditure of hospital. Mean age was 68.9 (±12.7) years and length of stay (LOS) was 10.9 (±7.9) days. In all, 345 patients (80%) had an ischemic stroke and 84 (20%) had a primary intracerebral hemorrhage. The direct in-hospital cost of all stroke patients, 1.551.445,00 €, accounted for a total hospitalisation of 4.674 days (331.9 € per day in hospital). The mean in-hospital cost per patient was 3.624,9 (±2695.4) €. The 59% of the total cost concerns the cost of "bed and staff", (6%) "pre-hospital cost", (13%) "laboratory investigations", (6%) "imaging investigations", (8%) "supportive nursing", (7%) "medication", (0.6%) "rehabilitation therapy" and (0.7%) "other expenses". Hemorrhagic strokes were significantly more expensive than the ischemic strokes (mean 5305.4 (±4204.8) € and 3214,5 (±1976.2) € respectively). Amongst ischemic stroke subtypes the mean total cost was significantly lower for lacunar strokes (2328.7±1100.2 €). The length of stay was highly correlated with in-hospital total cost. Multivariate linear regression model showed that the admission ward, stroke severity on admission, stroke type and status discharge were independent predictors of cost. In order to withhold the hospital cost, policies of administration that aiming to the reduction of length of stay should be taken into consideration.Τα ΑΕΕ είναι η πρώτη αιτία αναπηρίας και η τρίτη αιτία θανάτου παγκοσμίως. Επίσης οι ασθενείς με ΑΕΕ είναι οι συχνότεροι χρήστες των υπηρεσιών υγείας. Παράλληλα, στη χώρα μας δαπανάται ετησίως το 10% του Ακαθάριστου Εγχώριου Προϊόντος (ΑΕΠ) για την υγεία σε σχέση με το μέσο όρο του 8,9% των χωρών του Οργανισμού Οικονομικής Συνεργασίας και Ανάπτυξης (ΟΟΣΑ). Στόχος της μελέτης είναι η οικονομική αξιολόγηση του ενδο-νοσοκομειακού κόστους ασθενών με οξύ ΑΕΕ στην Ελλάδα καθώς επίσης και ο προσδιορισμός ανεξάρτητων παραγόντων που επηρεάζουν το κόστος νοσηλείας. Καταγράφηκαν δημογραφικά και κλινικά χαρακτηριστικά σε 429 συνεχόμενους ασθενείς με οξύ ΑΕΕ (ισχαιμικό ή αιμορραγικό) που εισήχθησαν σε όλες τις κλινικές του Πανεπιστημιακού Γενικού Νοσοκομείου Πατρών για διάστημα 18 μηνών. Υπολογίσαμε το κόστος, για κάθε ασθενή ατομικά, από την ώρα της εισβολής του ΑΕΕ έως την έξοδό του από το νοσοκομείο. Το κόστος μετρήθηκε σε ευρώ (€) και σύμφωνα με τις πραγματικές δαπάνες του νοσοκομείου. Η μέση ηλικία των ασθενών ήταν 68.9 (±12.7) έτη και η διάρκεια νοσηλείας ήταν 10.9 (±7.9) ημέρες. Οι 345 ασθενείς (80%) είχαν ισχαιμικό ΑΕΕ και 84 (20%) είχαν πρωτοπαθή ενδοεγκεφαλική αιμορραγία. Το άμεσο ενδο-νοσοκομειακό κόστος νοσηλείας όλων των ασθενών με οξύ ΑΕΕ ανήλθε στα 1.551.445,00 € για μια συνολική διάρκεια νοσηλείας 4.674 ημερών (331,9 € ανά ημέρα νοσηλείας). Το μέσο ενδο-νοσοκομειακό κόστος ανά ασθενή με ΑΕΕ ήταν 3.624,9(±2695.4) €. Το 59% του συνολικού κόστους αποδόθηκε στο κόστος "κλίνης και προσωπικού", (6%) "προ εισαγωγής", (13%) "εργαστηριακό έλεγχο", (6%) "απεικονιστικό έλεγχο", (8%) "αποκλειστική νοσηλευτική φροντίδα", (7%) "φαρμακευτική αγωγή", (0.6%) "θεραπεία αποκατάστασης" και (0.7%) "διάφορα έξοδα". Τα αιμορραγικά ΑΕΕ είχαν σημαντικά μεγαλύτερο κόστος από τα ισχαιμικά ΑΕΕ (μέσο 5305.4 και 3.214,5 €, αντίστοιχα). Μεταξύ των υπότυπων των ισχαιμικών ΑΕΕ το συνολικό μέσο κόστος ήταν σημαντικά χαμηλότερο για τα "κενοτοπιώδη" έμφρακτα (2328.7±1100.2 €). Η διάρκεια νοσηλείας είχε υψηλή συσχέτιση με το συνολικό ενδο-νοσοκομειακό κόστος. Η πολυπαραγοντική γραμμική ανάλυση παλινδρόμησης έδειξε ότι το τμήμα εισαγωγής, η βαρύτητα του ΑΕΕ στην εισαγωγή, ο τύπος του ΑΕΕ και η κατάσταση εξόδου ήταν ανεξάρτητοι παράγοντες του κόστους. Αν επιθυμούμε τη συγκράτηση του νοσοκομειακού κόστους, θα πρέπει να ληφθούν υπόψη πολιτικές διοίκησης που στοχεύουν στη μείωση της διάρκειας νοσηλείας
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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