Your interpretation is broadly correct. This is a TAM → SAM → SOM market sizing model for the UK SME cyber insurance market.

**Prompt 1 -** I’m building a market sizing for UK SME cybersecurity insurance. I want to estimate the TAM (excluding any businesses that are unaddressable because they’re not actually in operation), the penetrated market (SAM) and the volume of market opportunity every year from contracts coming to market (SOM). My model should cover the period 2020 to 2030. I have downloaded data from the ONS with UK business counts by industry and employee size. I would like one sheet that dynamically manages all of the mapping we need to do to prepare the ONS data with categories we can use in the model. I think we’ll want to group industries by their likelihood to need / purchase insurance and by size sub-categories within SME

*After this it gave me options to answer before proceeding*

**Prompt 2 -** Next make a separate assumptions sheet where we will collect volume growth rates, insurance penetration rates, premium pricing, price growth rates and contract lengths. Historical volume inputs will be taken directly from the ONS data, so there’s no need for assumptions here. For forecast growth rate of business by size category, assume the 2024/25 growth rate persists for the next 5 years. For the SOM, can we have an assumption line for average contract length. The volume potentially coming to market each year is then the SAM multiplied by 1 divided by the contract length. Of these renewals, a certain % change providers. Any new business wins (ie TAM consolidation) should already be captured by our penetration assumptions. These inputs will eventually be sourced from expert calls, survey results and public research, so just fill with sensible dummy data for now. This is the sheet that the model will link to for all its key assumptions. We'll build the model calculations after.

*Get rid of anything we think is overcomplicated that you think it has put in there*

**Prompt 3 -** OK, please proceed in laying out our 10 year model in a new tab. Build the sheet from top to bottom, so we start with volume inputs and end at the SOM.  Make sure every step is clear to follow and links to input data and assumptions sheet clearly. Have YoY growth rates for each category (e.g. Micro, Small, etc.) after the TAM, SAM and SOM £m calculations. Add 2 columns of 5 year CAGRs to summarise growth rates

*Make any clean ups needed to the methodology*

**Prompt 4** - Make a new tab with a bar that shows how much of the TAM is currently penetrated

**Prompt 5** - In a new tab can you set up a sensitivity table that shows the size of the Micro SAM by 2030 under some more aggressive penetration assumptions in the forecast period