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Massive Uncertainty

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... .5 0.0 Ratio of Actual to Estimated Cost CONST SAT m g HST GLL UARS GRO COBE MGL MOBS LSAT EUVE ERBE AVG St.Dev. 3.5 3.0 2 ... out Review of the ... – PowerPoint PPT presentation

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Title: Massive Uncertainty


1
Massive Uncertainty
  • Dr. Richard de Neufville
  • Professor of Engineering Systems and
  • Civil and Environmental Engineering
  • Massachusetts Institute of Technology

2
Massive Uncertainty
  • Objective To present realistic context of
    forecasting exercise
  • Topics
  • Evidence
  • Consequences

3
Causes of Uncertainty
  • Underlying variability of phenomenon
  • Difficulties in measurement or estimation
  • Unforeseen or unpredictable circumstances
  • Limits to valid measurement
  • for example behavioral patterns

4
Evidence
  • 1. Simple Physical Systems
  • 2. Overall Traffic
  • 3. Local Traffic (Worse)
  • 4. Other Operations

5
Ratio of Real Costs to Estimated Costs for
Airport Projects
Costs expressed in constant dollars
Median 1.25
Percent of Occurrences
Real/Estimated Cost Ratio
6
Cost Growth for Various Projects
3.0 2.5 2.0 1.5 1.0 0.5 0.0
Ratio of Actual to Estimated Cost
DOD60 HWAY WATER BLDNG DOD50 ADHOC MAJOR
ENRGY NASA NASA AVG St.Dev.
CONST SAT m g
7
NASA Projects Cost Growth
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
Ratio of Actual to Estimated Cost
HST GLL UARS GRO COBE MGL MOBS LSAT EUVE
ERBE AVG St.Dev.
8
Results of a 2004 study
Adapted from Terminal Area Forecast (TAF)
Accuracy Assessment Results Jerome Friedman,
MITRE CAASD, Sept. 30, 2004
9
Results of a 2004 study
Adapted from Terminal Area Forecast (TAF)
Accuracy Assessment Results Jerome Friedman,
MITRE CAASD, Sept. 30, 2004
10
Recent Error Data from U.S Source MITRE CAASD
and FAA
11
Recent Error Data from U.S Source MITRE CAASD
and FAA
12
Actual vs. Forecast 10 years earlier Source FAA
Aerospace Forecast FY 2006-2017
Note These are aggregate data, in which greater
local variations tend to cancel each other out
13
Older FAA Forecasts vs. Actual Data ( Difference)
Review of the FAA 1982 National Airspace System
Plan
14
Forecast vs. Actual International Pax in
Japan
15
Forecast vs. Actual International Pax to Japan
16
Forecast vs Actual International Pax in Sydney
17
  • ACTIVE GENERAL AVIATION AIRCRAFT
  • 1980 FORECAST

18
  • ACTIVE GENERAL AVIATION AIRCRAFT
  • 1985 FORECAST

19
  • ACTIVE GENERAL AVIATION AIRCRAFT
  • 1990 FORECAST

20
  • ACTIVE GENERAL AVIATION AIRCRAFT
  • 1998 FORECAST

21
Summary and Recommendations
  • Summary
  • Forecast Errors have been large
  • Likely to continue
  • Recommendations
  • Expensive Forecasting is cost-ineffective
  • Use general trends
  • ...With large ranges
  • Flexible Approach to Planning!!!
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