Time Series

1
Time Series

• Techniques and an Example from Roger Simons The
  City Building Process

2
What is a Time Series?

• Numerical data ordered by intervals of time in
  chronological order
• The analysis of a time series involves
  decomposing the series into its components, e.g.,
  
• Trends
• Cyclical and Seasonal Fluctuations
• Irregular Fluctuations

3
Example of a Time Series
1888 2
1889 29
1890 33
1891 40
1892 56
1893 43
1894 39
1895 21
1896 38
Etc 31
4
To Analyze a Time Series

• Identify the possible processes affecting the
  series
• Inflation or Deflation (for series of prices or
  expenditures)
• Long term trend
• Cyclical fluctuations
• Seasonal fluctuations
• Irregular fluctuations

5
Steps to Analyze Changing Construction Costs

• Identify a measure
• Construction Cost? Or.
• Construction Cost Per Square Foot
• Convert to Constant Dollars
• Measure the Trend
• Identify cyclical or seasonal factors
• Identify irregular fluctuations

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Raw Construction Cost over Time
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Properties Built over Time
8
Size of Buildings Built over Time
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Adjusting for Inflation

• if yrbuilt gt887 and yrbuilt lt 912 then let
  concost2concost20
• if yrbuilt gt911 and yrbuilt lt 916 then let
  concost2concost/.06
• if yrbuilt 916 then let concost2concost/.065
• if yrbuilt 917 then let concost2concost/.077
• if yrbuilt 918 then let concost2concost/.090
• if yrbuilt 919 then let concost2concost/.104
• if yrbuilt 920 then let concost2concost/.120
• if yrbuilt 921 then let concost2concost/.107
• if yrbuilt 922 then let concost2concost/.103
• if yrbuilt 923 then let concost2concost/.102
• if yrbuilt 924 then let concost2concost/.102
• if yrbuilt 925 then let concost2concost/.105
• if yrbuilt 926 then let concost2concost/.106
• if yrbuilt 927 then let concost2concost/.104
• if yrbuilt 928 then let concost2concost/.102
• if yrbuilt 929 then let concost2concost/.102
• if yrbuilt. then let concost2 concost 20
• if concost. Then let concost2 .

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Construction Cost Adjusted for Inflation
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Comparing Raw and Inflation Adjusted Construction
Costs
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Construction Cost per Square Foot (Inflation
Adjusted)
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Construction Cost per Square Foot (Inflation
Adjusted)
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The Model Cost per square foot constant(a)
b1year b2(last years cost per square foot)
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The Model Cost per square foot constant(a)
b1year b2last years cost per square foot

• Cost per square foot 7.33 .59 (last years
  cost) .29 (year)
• Number of cases 39 (1889-1928). 18891
• Adjusted R Square 77.2

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Trend and Residuals
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The Data1.Year 2. Cost Per Square
Foot3. Last Years Cost Per Square Foot4.
Predicted Cost5. Residual