STEM help / Calculation framework

Inputs beginning with ‘D’

Data 1, Data 2

A time series, initially copied from a model input, which has been identified as a Dimension parameter, and which can then be modified to capture differing scenario data.

Note: By default, the rows are labelled Data 1, Data 2, etc., but once a parameter has been associated with a Dimension or Template, then the row label changes to reflect the relevant field (e.g., Service1.Penetration.RefValue).

See 9. Model structure

Default: Constant {1.0}.

Death Period

Enables you to ‘switch off’ the curve (from zero). This can be a year, a quarter, a month, or even a fully-qualified date.

Default: Y-1.

Decommissioning Cost

The cost of removing a Resource from the network in the Calibration Period. It is better to model used or scrap value as a residual value, otherwise it will occur in the accounts as a negative operating cost.

Default: 0.0.

Decommissioning Cost Trend

This is applied to the calibration value you set for the Decommissioning Cost in the Resource/Costs dialog.

Default: Constant {1.0}.

Deploy Any Resource

A choice of whether Resources in the same Function are regarded as interchangeable for the purpose of Function deployment.

No: deployment constraints are applied to each Resource separately. The Function constraint is only applied to a particular Resource if it does not have a deployment constraint of its own, i.e. Sites defined as Location (<none>).

Yes: any individual Resource deployment constraints are applied, then the Function constraint (if any) is applied to all the Resources collectively.

Default: Yes.

Deploy With Utilisation

A choice of whether the deployment calculation should allow for the Maximum Utilisation and Minimum Slack inputs.

Yes: the geographical overhead is calculated on the basis of the Maximum Utilisation and Minimum Slack inputs being satisfied at each individual site.

No: the Maximum Utilisation and Minimum Slack constraints are checked independent of Deployment and only consider the total installation over all sites. (This was the only option prior to STEM 7.4 and will be set when an older model is loaded for backwards compatibility of the results.)

Default: Yes.

Deposit Rate

The annual interest rate for surplus cash on deposit as liquid, short-term investments (typically marketable securities). This is the benefit received by the network from funds on deposit.

All rates are specified as proportions, e.g., an interest rate of 10% is specified as 0.1.

Default: 0.0.

Depreciation Rate

The write-off rate for reducing-balance depreciation as a proportion, e.g., 0.25 means 25% of the capital value is written off each year. All the remaining value is written off when a Resource is removed from the network. The depreciation rate may be set to zero or any positive annual rate less than 100%. The default is –1, which is a special value indicating that straight-line depreciation should be used. This input is only meaningful for a persistent resource.

Default: –1.0.

Depreciation Schedule

A time series specifying how depreciation should be spread over the financial lifetime of a Resource.

Provides an alternative to the Straight Line or Reducing Balance options, and makes it possible to match any non-standard or statutory depreciation methods, such as Modified Accelerated Cost Recovery System (MACRS).

Default: Constant {1.0}. Equivalent to straight-line depreciation.

Discount Rate

The discount rate used to calculate the net present value (NPV) of the network. Prior to STEM version 7.4, this input was defined as a constant in the Results program, but now you can tailor the discount rate to a particular model (or client).

Note: Although the Editor will allow you to define the discount rate as a time-series, we strongly recommend that you leave it as a constant unless you are a specialist in corporate valuation and must consider a specific risk event in time.

Default: Constant {0.1}


A choice of the way in which Resources will be distributed across the Sites specified as part of a Function or Resource deployment constraint.

One for one: the number of sites represents the minimum number of units of Resources that must be deployed, i.e., there must be at least one unit per site.

Monte Carlo: this provides a good approximation of normal installation, and is the result of statistical analysis based on a normal distribution of customers over sites.

Homogeneous: demand is distributed evenly over the sites, and at least one unit of Resource is installed at each site. When all units are fully utilised, another unit is installed at each site.

Smoothed Homogeneous: units are installed to meet demand until one unit is installed at each site, representing a gradual spread of demand as capacity fills up. Once there is at least one Resource for each site, demand is distributed evenly, with the same number of units at each site.

Extended Monte Carlo: same as Monte Carlo, but at least one unit is provided per site.

Default: One for one.

Dividend Rate

The proportion of profit after interest and tax which is declared as dividends.

Default: Constant {0.0}. No dividends are declared.


When the Type of a Sensitivity is set to Proportion, determines the proportion by which the value of a parameter is decreased (e.g., 1%).

When Type is set to Delta, specifies the fixed amount by which the value of the parameter is decreased (e.g., 10,000).

When Type is set to Absolute, specifies the minimum value of the parameter (e.g., 1000).

See 9.4 Using sensitivities to identify critical model assumptions.

Default: Constant {0.00}.


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