Modelling the impact of OPA 90 and double hull technology on oil spill numbers

1. Modelling the impact of OPA 90 and double hull technology on oil spill numbers David Glen London Metropolitan University Presented to IMSF Annual Conference Gdansk, April 2008

2. Outline • Literature Review • Model • Estimation & Results • Conclusion

5. Literature Review • Talley & Anderson (1995),Talley Jin, and Kite Powell (2001) • Spills as a function of vessel size, vessel damage severity, and 'regulatory effort' • Homan and Steiner (2008) • Spills as a function of traffic volume, nos. of tankers, average tanker size, real oil price, and repair costs

6. Literature Review (2) • HS model – Poisson Count model of spill numbers pre and post 1991 (OPA introduction) • Model applied to US Coastguard Data • Found – variables gave reasonable fit. • Post 1991 –the OPA effect • % of tankers with double hull technology • Dummy variable measuring OPA introduction • Found both these to be significant in explaining the reduction in spill numbers post 1991

7. So can we model the ITOPF data in the same way? Source: www.itopf.org – Oil spill statistics - accessed January 2008

8. 1970 - 1990 Tonne mile data Real oil price Average tanker size Tanker lay up % 1970 - 2005 As left hand column plus Double hull fleet % Dummies for OPA MarPol ISM Data and Model

9. Model Estimation • Poisson Count Model • Tested for 'overdispersion' (mean and variance of spill numbers should be the same value in a PC model) • Used negative binomial model when overdispersion present • (Models used because dependent variable takes positive or zero values) • Applied to All Spills, 'Small Spills' and 'Large Spills' as per ITOPF definitions

10. Results

11. Results

12. Principal Results • Model variables all 'statistically significant' • Real oil price differs in sign from HS • Double Hull % highly significant • Dummy variables – MarPol/ISM/OPA all insignificant so not reported • Increase in recent accidents driven by increase in world trade tonne miles

16. Summed Up Note: Spill totals rounded to nearest whole spill, hence discrepancies in totals

17. Conclusion • Oil spills significantly reduced by double hull technology • No evidence found for other effects • Trade is a key driver • Model based on relatively few observations, so may not be robust

18. Instead of this, then perhaps we might get....

19. ships as green as this one in the future • Thank you for your attention!