simulating virginia’s state responsible confined...
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Simulating Virginia’s State Responsible Confined Forecast
Tama S. Celi, Ph.D.Research & Forecast Manager
Virginia Department of [email protected]
Forecasting in Virginia
• Appropriations Act requires a Consensus process that is overseen by the Secretary of Public Safety.
• Participants: Department of Corrections, Department of Juvenile Justice, Department of Criminal Justice Services, Compensation Board, Department of Planning and Budget, Joint Legislative Audit and Review Committee, State Police, VA Supreme Court and the Criminal Sentencing Commission.
• Consensus Process includes:– Technical Committee; technical experts from associated agencies review and vote on
competing models.– Liaison Committee; middle managers from associated agencies review and make
recommendations based on any impending internal policy or procedural changes.– Policy Committee; policy makers and agency heads review and make adjustments based on
impending policy changes.• Major Topics
– Trends– Admissions– Confined– Accuracy
Virginia Department of CorrectionsResearch & Forecast Unit
October 20122
Why Change?Need for More Information and transparency• Changing policy• New data systems• Reversals in trends
Issues with Old Model• Based on the Parole system (abolished in VA in 1995) using information from released
offenders (i.e. percent of sentence served)• Assumed normal distributions among the Most Serious Offense (MSO) groups
– Assigned Minimum, Mean and Maximum Sentence (in months) for each offense group– Example: Assault MSO (Min=12.0, Mean=51.9, Max=684.0) but the Median was 34.0 months
• 71% of Assaults have a sentence <52.0 months (MSOs are not normally distributed)
– Impact: Old Model was keeping offenders too long, resulting in erroneously high forecasts
• When no female data was available to put into the model, called for male data to be used
• When no offenders existed for a particular group, assumed 1000 and used the last year’s profile information
Virginia Department of Corrections Research & Forecast Unit October 2012 3
Policy Changes
• Parole was abolished in Virginia in 1995.
• As inmates sentenced under Truth‐in‐Sentencing (TIS) have become the majority of the DOC confined population (~84%), simulation modeling has become a more powerful forecasting tool than ever before.
• The surety of Length of Stay (LOS) of TIS sentences provides concrete information upon which to build the model. Release dates are calculated and known when the inmate is admitted to the DOC and these dates are available for use in forecast.
Virginia Department of Corrections Research & Forecast Unit October 2012
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• Strengths– Uses Estimated Release Date (ERD) of the ~37,000 current inmates
– Uses the most current sentencing/LOS information for future Admissions
• Weaknesses– If the Admissions forecasts are “OFF”; the simulation model will be similarly “OFF”
– As with other methods, if sentencing policy or practice for future Admissions or Release change substantially, the simulation model will not capture that change until future years
Virginia Department of Corrections Research & Forecast Unit October 2012 5
VA DOC Simul8 Model
Day 0: Existing Confined Population is loaded into the model• Number is End of Month (EOM) population of Day 0• Profiles are based on existing Confined Population
Special Release Calculations base on Probability: As they are imported into the model, each inmate has a date for Death and Other* Release calculated. If PE, a Discretionary Release Date is also calculated.
• Death:– Males – 3 year average rates based on age and race– Females – 3 year average rate applied randomly (no significant patterns identified)
• Other:– Males – most recent year’s release rates applied randomly by crime type (V/PPO/D)– Females – most recent year’s release rate applied randomly
• Discretionary Parole: Parole Board Grant Rates by gender and crime type for the latest year are used since discretionary release rates change from year to year
How the VA DOC Simul8 Model Works
*Includes Release by Court Order, Pardon/Commutation, etc.
Virginia Department of Corrections Research & Forecast Unit October 2012 6
Confined inmates are released on their Expected Release Date(ERD) starting on Day 1 unless:
• IF Death Date < ERD, Other Date and Discretionary Date; THEN Released on Death Date
• IF Other Date < ERD, Discretionary Date and Death Date; THEN Released on Other Date
• IF Discretionary Date < ERD, Other Release Date and Death Date; THEN Released on Discretionary Date
How the VA DOC Simul8 Model Works
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How the VA DOC Simul8 Model Works• Admissions begin to enter on Day 1• NCC forecasts are distributed into more specific offense groups
• Total Admissions = NCC + Parole Violators • The model randomly chooses among similar recent admissions to derive a profile for future new Admissions
• ERD is calculated based on Total Expected Length of Stay (TELOS)* of profile assigned to each Admission
Virginia Department of Corrections Research & Forecast Unit October 2012 8
*TELOS = (Expected Release Date – New Commit Date) for NCC;TELOS = (Expected Release Date – Revocation Date) for Parole Violators
How the VA DOC Simul8 Model Works
• As Admissions enter, each inmate has a date for Death and Other Release calculated. If PE, a Discretionary Release Date is also calculated.
• Admissions are released on calculated ERD unless:– IF Death Date < ERD, Other Date and Discretionary Date; THEN Release
on Death Date
– IF Other Date < ERD, Discretionary Date and Death Date; THEN Release on Other Date
– IF Discretionary Date < ERD, Other Release Date and Death Date; THEN Release on Discretionary Date
Virginia Department of Corrections Research & Forecast Unit October 2012 9
Expected Release Dates*
• For Current TIS Inmates, Good Time Expected Release Date (ERD) is used
• For Current PE Inmates, Mandatory Parole Release Date is used
• For Future Admissions, TELOS for most recent Admissions is used to calculate Expected Release Date
*Date an inmate is expected to be released based on the current rate at which he is earning good time credits
Virginia Department of Corrections Research & Forecast Unit October 2012 10
VADOC Simul8 Model
Virginia Department of Corrections Research & Forecast Unit October 2012 11
Testing the New Model
• In order to be able to test the model, in 2010, we re‐ran the 2007 Forecast with the simulation model using 3 scenarios:– The actual admissions for the known period supplemented with the 2007 admissions projections
– The adopted 2007 admissions projections– The actual admissions for the known period supplemented with the 2010 admissions projections
Virginia Department of Corrections Research & Forecast Unit October 2012 12
Comparison of ForecastsActual EOM
Adopted 2007
Forecast
Adopted 2008
ForecastSimlu8 Actual/ 2007 Forecast
Simul8 2007 Forecast
Simul8 Actual/ 2010 Forecast
FY2008 38,826 39,347 38,825 39,285 38,845
FY2009 38,387 40,305 39,621 38,280 39,942 38,270
FY2010 37,724 41,292 40,563 37,790 40,497 37,645
FY2011 37,503 42,399 41,552 39,685 41,247 37,343
FY2012 37,159 43,559 42,527 41,094 42,075 37,277
FY2013 44,744 43,526 42,511 43,175 37,556
Avg Growth Rate -1.1% 2.6% 2.4% 1.9% 1.9% -0.7%
Average Monthly Absolute Error
Adopted 2007 Forecast
Adopted 2008 Forecast
Simlu8 Actual/ 2007 Forecast
Simul8 2007 Forecast
Simul8 Actual/ 2010 Forecast
FY2008 172 64 142 70
FY2009 1,309 614 73 1,103 87
FY2010 2,808 2,173 112 2,283 118
FY2011 4,390 3,580 1,319 3,339 79
FY2012 5,858 4,833 3,297 4,522 150
Avg Annual Error 2,907 2,800 973 2,279 101
Virginia Department of Corrections Research & Forecast Unit October 2012 13
Comparison of Forecasts
35,000
37,000
39,000
41,000
43,000
45,000
Jul-05 Jan-06 Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Jan-09 Jul-09 Jan-10 Jul-10 Jan-11 Jul-11 Jan-12 Jul-12 Jan-13
Actual EOM
Adopted 2007 Forecast
Adopted 2008 Forecast
Simlu8 Actual/2007 Forecast
Simul8 2007 Forecast
Simul8 Actual/2010 Forecast
Virginia Department of Corrections Research & Forecast Unit October 2012 14
Comparison of Forecasts
Virginia Department of Corrections Research & Forecast Unit October 2012 15
30,000
32,000
34,000
36,000
38,000
40,000
42,000
44,000
46,000
48,000
50,000
Jan‐00Jul‐00Jan‐01Jul‐01Jan‐02Jul‐02Jan‐03Jul‐03Jan‐04Jul‐04Jan‐05Jul‐05Jan‐06Jul‐06Jan‐07Jul‐07Jan‐08Jul‐08Jan‐09Jul‐09Jan‐10Jul‐10Jan‐11Jul‐11Jan‐12Jul‐12Jan‐13Jul‐13Jan‐14Jul‐14Jan‐15Jul‐15Jan‐16Jul‐16Jan‐17Jul‐17Jan‐18
SR Pop
ulation
EOM
Actual EOM
2004 Forecast (Prophet)
2005 Forecast (Prophet)
2006 Forecast (Prophet)
2007 Forecast (Prophet/DPB)
2008 Forecast (DPB)
2009 Forecast (DPB)
2010 Forecast (Simul8)
2011 Forecast (Simul8/DPB)
2012 Forecast 1 (Simul8)
2012 Forecast 2 (Simul8)
2012 Forecast 3 (Simul8)
Tools for Development & Validation
• Customized output is exported into Excel to provide information on admissions, releases by type, etc.– Releases forecasted by regular releases, mandatory parole, discretionary parole, death and other
– Admissions are counted– Results split by gender and offense types
• Start with running back in time to validate, then move the start date to the relevant forecast period
Virginia Department of Corrections Research & Forecast Unit October 2012 16
Producing Forecasts
• Running the model– Produces result of single run through the chosen forecast period
– Used for development, validation and testing
• Trials– Multiple runs that produce confidence interval and mean– This is what is done to produce a forecast– Trials can take considerable time
Virginia Department of Corrections Research & Forecast Unit October 2012 17
Other Uses
• Subpopulation Forecasts: use to produce a Sexually Violent Predator (SVP) Predicate Release Forecast
• Legislative Impact Analysis: Can adjust populations to reflect potential policy changes
• Potential Future Uses– Tool for planning types of beds needed– Tool to determine resource needs– Tool to develop reentry planning– Expand forecasts to predict Community Corrections population– Develop micro‐models for resource allocation, staff
development and operational needs
Virginia Department of Corrections Research & Forecast Unit October 2012 18