Dr. Celal Aksu HOME PERSONAL TEACHING SERVICE



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R e s e a r c h  I n t e r e s t s

Portrait of Celal Aksu

Brief, expository descriptions of Dr. Celal Aksu's current research interests are provided below. Any related previous journal publications and current unpublished working papers by Dr. Aksu are also referenced. For related presentation papers, please see the Vita section.



 

Issues Regarding Accounting Earnings and Firm Valuation


Related papers:

"An Empirical Investigation of the Causal Relationship between Stock Prices and the Short Ratio". Co-author: Erdal Gunay.

"An Empirical Analysis of the Causal Relationship Between Short Interest and Stock Prices." Journal of Business Finance & Accounting, July, 1995. Co-author: Erdal Gunay.

"Economic Benefits, Informativeness and Value-Relevance of Troubled Debt Restructurings: Some Evidence and Policy Implications." Co-author: Mine H. Aksu.

"Prediction of Successful Troubled Debt Restructurings (TDR) and Excess Returns from TDR Profiles." Co-author: Mine H. Aksu.

"Time Series Properties and Forecasting of Quarterly Cash Flows."


Modelling and Forecasting Financial Time Series in the Presence of Outliers and Structural Changes

Earnings forecasts play a major role in several decision contexts such as equity valuation, acquisitions or divestitures, evaluation of accounting method changes, design of executive compensation plans, and performance evaluation of management. Previous research indicates that accurate forecasts of earnings could not be obtained using time-series techniques. This is mainly attributed to estimation biases and sampling errors due to small sizes of the samples used, and to the presence of outliers and structural changes in time series of earnings that adversely affect the model identification tools.
   Dr. Aksu's interests are in modeling and forecasting accounting earnings and other financial time-series using new procedures and software that have been developed in recent years for detecting and adjusting for outliers and structural changes.

Related papers:

"Modeling and Forecasting Quarterly Accounting Earnings in the Presence of Outliers and Structural Changes."

"Time-Series Properties, Adjustment Processes and Forecasting of Financial Ratios." Journal of Accounting, Auditing & Finance, Winter, 1996. Co-authors: Claire Eckstein, William H. Greene, and Joshua Ronen.


Forecast Accuracy Measures

In the context of forecasting, the relevant measure of performance to select among forecasting or forecast combination models is the efficiency (accuracy) of the ex-ante forecasts. Dr. Aksu's research interests in this area involve: i) evaluation of the desirable properties of forecast error measures, and ii) design and development of a methodology to create new error measures specially for evaluating combined forecasts.
   The focus on combination error measures is based on the arguments that such error metrics should be more sensitive, less outlier-independent, less stable, and less "typical" than original forecast error measures, and should possess an additional "conservatism" property.

Related papers:

"A Framework for Evaluating and Developing Forecast Error Measures." Co-author: Sevket I. Gunter.


Combining Forecasts

A linear combination of forecasts obtained from models which may use different functional forms and/or information sets usually outperform individual forecasts. Although the superiority of nonnegativity restricted least squares (NRLS) combinations to ordinary least squares and equality restricted least squares combinations are demonstrated theoretically in Dr. Aksu's papers, there is only limited supporting empirical evidence.
   Dr. Aksu is interested in i) providing convincing empirical evidence of the superiority of NRLS combination models, ii) providing combined forecasts which outperform analysts' forecasts of accounting and financial time series, and iii) developing new robust regression-based heuristic combination methods which preserve the characteristics of the NRLS technique while minimizing its computational burden.

Related papers:

"Regression Based Robust Combinations of Forecasts." Co-author: William Wei.

"Usefulness of Heuristic N(E)RLS Algorithms for Combining Forecasts." Journal of Forecasting, November, 1997. Co-author: Sevket I. Gunter.

"Efficiency of Combinations of Forecasts Using Inequality Restricted Least Squares." Economic and Financial Modelling, Spring, 1994. Co-author: Sevket I. Gunter.

"An Empirical Analysis of the Accuracy of SA, OLS, ERLS, and NRLS Combination Forecasts." International Journal of Forecasting, June, 1992. Co-author: Sevket I. Gunter.

"N-Step Combinations of Forecasts." Journal of Forecasting, July-September, 1989. Co-author: Sevket I. Gunter.

 


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