Demand Forecasting for Inventory Control

188 Pages·2015·6.4 MB·English

by  Nick T. Thomopoulos (auth.)

Demand Forecasting for Inventory Control
Nick T. Thomopoulos
Demand Forecasting
for Inventory Control
1 3
Nick T. Thomopoulos
Stuart School of Business
Illinois Institute of Technology
Burr Ridge
Illinois
USA
ISBN 978-3-319-11975-5 ISBN 978-3-319-11976-2 (eBook)
DOI 10.1007/978-3-319-11976-2
Library of Congress Control Number: 2014954807
Springer Cham Heidelberg New York Dordrecht London
© Springer International Publishing Switzerland 2015
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For my wife, my children, and my grandchildren
v
Preface
Looking back over my working years, I was most fortunate with the background
gained as it happened to unfold from year-to-year in both industry and in academia.
This included working in industry at International Harvester as supervisor of opera-
tions research in the corporate headquarters; at IIT Research Institute (IITRI) as a
senior scientist serving as a consultant to international industry and government;
as a professor in the Industrial Engineering Department at the Illinois Institute of
Technology (IIT) and also in the Stuart School of Business at IIT My experience
with FIC Inc., a software company, is where I gained knowledge on the software
tools needed in industry, as well as the customers’ call for user friendly tools. For
many of the years, I was privileged to serve as consultant to a wide variety of in-
dustries in the United States, Europe and Asia. At IIT, I was fortunate to be assigned
an array of courses, gaining a wide breadth with the variety of topics, and with the
added knowledge I gained from the students and with every repeat of the course.
I also was fortunate to serve as the advisor to 36 bright Ph.D. students as they car-
ried on their dissertation research. Bits of knowledge from the various courses and
research helped me in the classroom, in research, and also in my consulting assign-
ments. When I could, I used my industry knowledge in classroom lectures so the
students could see how some of the textbook methodologies actually are applied in
industry. At the same time, the knowledge I gained from the classroom helped me
to formulate and develop solutions to industry applications as they unfolded. The
wide variety of experience allowed me to paint a picture on which quantitative tools
really are useful in industry. This book is based on this total experience and also in-
cludes the demand forecasting methods that I found doable and helpful to industry.
Thanks foremost to my wife, Elaine Thomopoulos, who has encouraged me to
write this volume. She inspired and gave consultation very often as the need called.
Thanks also to the many people who have helped and inspired me along the way.
I can name only a few here. Raida Abuizam (Purdue University—Calumet), Brian
Ahearn (Komatsu Dresser), Wayne Bancroft (Walgreens), Owen Baxter (Wolver-
ine World Wide), Fred Bock (IIT Research Institute), Harry Bock (Florsheim Shoe
Company), Randy Braun (Komatsu Dresser), Toemchai Bunnag (PTT Public), John
Cada (Florsheim Shoe Company), Dan Cahill (International Truck and Engine),
Debbie Cernauskas (Benedictine University), Edine Dahel (Monterey Institute),
vii
viii Preface
John DeMotts (International Harvester), Frank Donahue (Navistar), Nick Faklis
(Patterson Office Supplies), Jim Gleason (International Harvester), Mark Graham
(International Truck and Engine), Scott Halligas (Florsheim Shoe Compnay), Jim
Harrington (International Harvester), Willard Huson (Navistar), Dick Ilseman (In-
ternational Truck and Engine), Marsha Jance (Indiana University—Richmond),
Tom Lewis (International Harvester), Carol Lindee (Panduit), Keith Mahal (Navi-
star), Nick Malham (FIC Inc.), Craig Marasek (Komatsu Dresser), Pricha Pan-
tumsinchai (M-Focus), Ted Prenting (Marist Colllege), Athapol Ruangkanjanases
(Chulalongkorn Univeristy), Doloris Santucci (Navistar), Mark Spieglan (FIC Inc.),
and Toli Xanthopoulos, (Mercer Investment Consulting).
Contents
1 Demand Forecasting for Inventory Control ............................................ 1
1.1 Introduction ......................................................................................... 1
1.1.1 Demand Forecasting ................................................................ 1
1.1.2 At the Beginning ..................................................................... 2
1.1.3 Calculators ............................................................................... 2
1.1.4 Data Processing ....................................................................... 3
1.1.5 Forecasting Pioneers ............................................................... 3
1.1.6 Computer Era .......................................................................... 4
1.1.7 Qualification ............................................................................ 4
1.2 Chapter Summaries ............................................................................. 5
2 Demand History ......................................................................................... 11
2.1 Introduction ......................................................................................... 11
2.2 Customer Demand History for a Part .................................................. 12
2.3 Demand-to-Date .................................................................................. 12
2.4 Service Part Regular and Emergency Demands .................................. 13
2.5 New and Replenish Stock Demands for Retail Items at DC ............... 13
2.6 W eekly Demands ................................................................................. 14
2.7 445 Fiscal Months at Plants ................................................................ 14
2.8 R egular Demands and Other Requirements at DCs ............................ 15
2.9 Regular and Promotion Demands at DCs and Stores .......................... 16
2.10 A dvance Demands ............................................................................... 16
2.11 Demand Patterns ................................................................................. 16
2.12 Return Demands .................................................................................. 17
2.13 Outlier Demands ................................................................................. 18
2.14 Coefficient of Variation ....................................................................... 18
2.15 Demand Distribution ........................................................................... 18
2.16 Cumulative Round Algorithm ............................................................. 19
2.17 Cumulative Forecasts .......................................................................... 19
2.18 Inventory Profile ................................................................................. 19
Summary ...................................................................................................... 21
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x Contents
3 Horizontal Forecasts .................................................................................. 23
3.1 Introduction ......................................................................................... 23
3.2 Horizontal Forecasts ............................................................................ 23
3.3 Raw Forecasts ..................................................................................... 24
3.4 Cumulative Rounding Algorithm ........................................................ 24
3.5 E stimate the Level ............................................................................... 25
3.6 Raw Forecasts ..................................................................................... 25
3.7 Integer Forecasts ................................................................................. 25
3.8 Standard Deviation and Cov ............................................................... 26
3.9 Horizontal Moving Average Forecasts ................................................ 27
3.10 Standard Deviation and Cov ............................................................... 27
3.11 Horizontal Discount Forecasts ............................................................ 29
3.12 Standard Deviation and Cov ............................................................... 30
3.13 Horizontal Smoothing Forecasts ......................................................... 32
3.14 Standard Deviation .............................................................................. 33
3.15 2-Stage Forecasts ................................................................................ 34
3.16 Raw Lines to Integer Forecasts ........................................................... 35
3.17 Integer Lines to Integer Forecasts ....................................................... 38
Summary ...................................................................................................... 39
4 Trend Forecasts .......................................................................................... 41
4.1 Introduction ......................................................................................... 41
4.2 T rend Regression Forecast .................................................................. 41
4.3 T rend Discount Forecasts .................................................................... 45
4.4 Trend Smoothing Forecasts ................................................................. 49
4.5 Dampening .......................................................................................... 53
4.6 Linear Trend Forecast Model .............................................................. 53
4.7 G eometric Forecast Model .................................................................. 54
4.8 M aximum Forecast Model .................................................................. 55
4.9 Other Dampening Applications ........................................................... 57
Summary ...................................................................................................... 57
5 Seasonal Forecasts...................................................................................... 59
5.1 Introduction ......................................................................................... 59
5.2 Seasonal Multiplicative Model ........................................................... 59
5.3 Revised Forecasts ................................................................................ 65
5.4 Initialize with 12-Months of Demand History .................................... 66
5.5 Seasonal Additive Model .................................................................... 67
5.6 Initialize With 12-Months of Demand History ................................... 68
5.7 Revision Forecasts .............................................................................. 68
Summary ...................................................................................................... 69
6 P romotion Forecasts .................................................................................. 71
6.1 Introduction ......................................................................................... 71
6.2 P romotion Horizontal Model .............................................................. 71
6.3 Initialize Stage ..................................................................................... 72
Contents xi
6.4 Standard Deviation and Cov ............................................................. 75
6.5 Forecasts ............................................................................................ 75
6.6 Revision Stage ................................................................................... 76
6.7 Unbiased Estimates ........................................................................... 76
6.8 Promotion Trend Model .................................................................... 78
6.9 Initialize Stage ................................................................................... 79
6.10 S tandard Deviation and Cov ............................................................. 81
6.11 Revision Stage ................................................................................... 84
6.12 Unbiased Estimates ........................................................................... 84
Summary .................................................................................................... 87
7 Multi-SKU Forecasts ............................................................................... 89
7.1 Introduction ....................................................................................... 89
7.2 S KU Mean and Standard Deviation .................................................. 90
7.3 D erivation of Binomial When n is a Random Variable ..................... 91
7.4 T op-Down Forecasting Method ........................................................ 92
7.5 T otal Demand Forecasts .................................................................... 92
7.6 L ocation Portion of Demand ............................................................. 93
7.7 T he Level by Location and Total ...................................................... 94
7.8 S tandard Deviation by Location and Total ........................................ 95
7.9 C ov by Location and Total ................................................................ 97
7.10 B ottom-Up Forecasting Method ....................................................... 97
7.11 L ocation j Forecasts .......................................................................... 98
7.12 Bottom-Up Total Forecast ................................................................. 99
7.13 T otal Forecast at Month 1 .................................................................. 101
7.14 H orizontal SKU Forecasts ................................................................. 102
7.15 S KU Forecasts at the Distribution Center ......................................... 103
7.16 S KU Forecasts at the Stores .............................................................. 105
Summary .................................................................................................... 106
8 Forecast Sensitivity .................................................................................. 107
8.1 Introduction ....................................................................................... 107
8.2 Cov by NMH when Horizontal Demands and Forecasts .................. 107
8.3 C ov by NMH when Trend Demands and Forecasts .......................... 108
8.4 C ov by Parameter and Forecast Model when
Horizontal Demands .......................................................................... 110
8.5 C ov by Parameter and Forecast Model when Trend Demands ......... 111
8.6 C ov by Parameter and Forecast Model when Seasonal Demands .... 112
8.7 C ov when Horizontal Demands with an Outlier ............................... 113
8.8 C ov when Trend Demands with an Outlier ....................................... 115
Summary .................................................................................................... 117
9 F iltering Outliers ...................................................................................... 119
9.1 Introduction ....................................................................................... 119
9.2 Horizontal Filtering ........................................................................... 119
9.2.1 H orizontal Filtering Algorithm (HFA) .................................. 120