STEM help / Calculation framework

Inputs beginning with ‘P’

Pass On Churn

A choice of whether the effective Churn Proportion for a Transformation is passed on to any other Transformations which take this Transformation as an Input.

No: the Output of this Transformation has no associated churn when used as an Input to another Transformation.

Yes: the effective Churn Proportion of this Transformation is used in the calculation of the effective Churn Proportion for another Transformation which takes this Transformation as an Input.

Default: No.

Past-Usage Significance

A discount factor governing the responsibility of Services for the costs of slack Resources which were previously used by those Services.

Slack costs are allocated to Services on the basis of their historical usage of a Resource, where usage in previous years is progressively discounted. For example, a factor of 0.5 would mean that only half of last year’s usage (and only one quarter of the preceding year’s usage) would be counted.

Slack costs are allocated on this basis, either when Resource capacity first becomes slack, or every year, depending on the Reallocation of Costs input.

Default: 0.0. Slack costs are allocated only on the basis of current-year usage.


The proportion of a Service’s Customer Base taking up the service. This can be defined directly as a time series, or as a reference to a separate Transformation element.

Default: Constant {1.0}. All potential customers are connected.


Specifies a particular period when the Value should apply. This can be a year, a quarter, a month, or even a fully-qualified date.

Default: Y0.

Period A

The period in which Value A applies. This can be a year, a quarter, a month, or even a fully-qualified date.

Default: Y0.

Period B

The period in which Value B applies. This can be a year, a quarter, a month, or even a fully-qualified date.

Default: Y0.


Determines the direction in which the parameter is varied. By default, a parameter is perturbed both up and down (Bidirectional), but you can choose to vary it in a single direction (Unidirectional) – in which case only the Up value is used (note that this value can be entered as a negative figure).

See 9.4 Using sensitivities to identify critical model assumptions.

Default: Bidirectional.

Physical Lifetime

The number of years a Resource lasts before it must be replaced. Its Physical Lifetime may exceed its Financial Lifetime, i.e., the Resource may be written off before the end of its Physical Lifetime. Effectively describes a shelf life for a consumable resource.

Default: 1.

Planned Units

A time series specifying a minimum total installation of a resource.

Default: Constant {0.0}.

Pre-Run Installation

A choice governing the installation of equipment in the first period of the model run.

Yes: a range of different ages of each Resource are installed according to the respective per-Resource Installation Profiles.

No: the profiles are disregarded and all equipment is installed brand new.

Default: No.

Price Elasticity

Controls the extent to which a change in a tariff introduces a change in demand. For the particular value of 1, demand changes in inverse proportion to tariff.

Default: Constant {0.0}. Demand is not affected by tariff.

Price List

An interpolated series specifying a number of cost breakpoints. The Quantity inputs specify the number of units of the Resource, while the Cost inputs specify the corresponding total costs, costs, or discount factors (depending on the Type setting).

Default: none. The default Price List is empty, meaning that it has no influence on the calculation of unit cost.

Prior Annual Loss

Losses carried forward from the years immediately before the start of the model, used to calculate the initial tax relief available if the network makes a profit in the early years of the model run. Only values in a period, governed by the input Tax Relief Years, up to and including year –1 will affect the calculations, even if the input Tax Relief Regime = Unlimited. For example, with Tax Relief Years = 5 and Prior Annual Loss = Constant {100.0}, the total accumulated losses available in year zero will be 500. Ignoring the actual profit or loss in the following years, this relief will reduce by 100 each subsequent year if Tax Relief Regime = Limited, whereas with Unlimited it will remain at 500.

Default: Constant {0.0}.

Production Function

A choice of whether the Capital Cost Structure of a Resource may change in time as individual Cost Index Cost Trends vary.

Zero Elasticity: the proportion of the Capital Cost associated with each Cost Index in the Calibration Period remains constant throughout the model run.

Cobb-Douglas: the unit Capital Cost is minimised in other years through substitution between increasing and decreasing trends, by varying the proportions associated with each Cost Index.

Default: Zero Elasticity.

Prop. Of Traffic in Busy Hour

The proportion of daily traffic that will be carried by a Service in the busy hour, used as part of the calculation of busy-hour traffic from annual traffic.

Default: Constant {0.2}. Assumes that 20% of the total daily traffic is carried during the busy hour.

Provision Cost

The one-off cost of providing a new connection to a Service in the Calibration Period (e.g., assigning a number, setting up billing) independent of Resources used.

Applies to all new connections to a Service, including those caused by churn.

Default: 0.0.

Provision Cost Trend

This is applied to the Provision Cost calibration value you set for each Service in the Administrative Costs dialog.

Default: Constant {1.0}.

Provision Trend

A time series representing the relative development of the Provision Cost throughout the model run.

Default: Constant 1.0.


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