Greg Dietzen

FCAS, MAAA

Consulting Actuary

San Francisco, CA, US

Greg Dietzen is a consulting actuary with the Property and Casualty Practice in Milliman’s San Francisco office. He joined the firm in 2015.

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Experience

Greg is actively involved in property insurance ratemaking and product development, particularly for catastrophe-exposed lines of businesses. He manages the San Francisco office's flood R&D efforts.

Greg’s areas of expertise include:

Rate and product development for private passenger automobile, homeowners, and private flood lines, including development of new rates and improved segmentation of current rates utilizing traditional actuarial methods and other predictive modeling techniques such as Generalized Linear Models
Catastrophic risk analysis, including catastrophe model review and validation
Incorporation of Geographic Informations Systems (GIS) data into rate development, underwriting, and portfolio visualization
Rate adequacy analyses, including on-leveling premium to current rates, calculating policyholder dislocation as a result of proposed rate changes, and calculating premium and coverage trends
Multi-state implementation of major rating plan updates and new programs

Prior to joining Milliman, Greg was an actuary with GEICO, specializing in private passenger automobile ratemaking.

Publications and Presentations

Greg has given presentations on the validation and use of catastrophe models, consumer demand in the flood insurance market, impacts of sea level rise on coastal communities, and the use of GIS in catastrophe ratemaking. Greg has published an article about the validation and use of catastrophe models.

Professional Designations

Fellow, Casualty Actuarial Society
Member, American Academy of Actuaries

Education

BS, Mathematics, United States Naval Academy
SM, Mechanical Engineering, Massachusetts Institute of Technology

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Publications

Read their latest work

Article

Geocoding for insurance: Why location matters in risk pricing

01 December 2025 - by Mia Wafer, Greg Dietzen, Garrett Bradford

We examine how geocoding processes that include multiple levels of spatial resolution can lead to more accurate quantification and pricing of risk.

Article

Advanced analytics in insurance: Utilizing building footprints derived from machine learning and high-resolution imagery

30 April 2025 - by Greg Dietzen, Garrett Bradford, Kailey Adams, Claire Palmer

High-resolution imagery in property insurance can identify unique exposures, such as roof characteristics and tree overhang, helping produce fairer premiums.

Article

Estimating undisclosed flood risk in real estate transactions

16 January 2025 - by Larry Baeder, Sean Gao, Greg Dietzen

Over 15 years, the average buyer of a previously flooded home can expect to incur more than $28,000 in flood damage, according to our report on flood risk.

Article

Taking catastrophe models out of the black box

25 July 2022 - by Greg Dietzen, Matt Chamberlain

As P&C insurers face a greater number of natural disasters with a warming planet, catastrophic models can help the industry better understand climate risk

Greg Dietzen

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Experience

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Read their latest work

Geocoding for insurance: Why location matters in risk pricing

Advanced analytics in insurance: Utilizing building footprints derived from machine learning and high-resolution imagery

Estimating undisclosed flood risk in real estate transactions

Taking catastrophe models out of the black box

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Greg Dietzen

Experience

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