Default Rules for Breakback

The fundamental rule for breakback is that changes are allocated to variables in a formula in direct proportion to their initial values. In other words, the more you have initially the more you get. This is what the program does in the absence of any other rules you might set.

Breakback will not work over built in functions or conditional formulas.

In the event of a profile that contains mixtures of zeros and values, zeros remain at zero, the remainder being allocated pro rata across the other variables.

For formulas with a mixture of additions and subtractions, the rule increases the items that are additions, and decreases the items that are subtractions by an amount proportional to the initial values. For example, suppose a D-List contains the formula:

Consider a simple example containing straight addition of detail items. A simple D-List contains four detail items and a total. The formula for the total is

Company Total = North + South + East + West

Likewise, a Periods D-List is also used where

Period 1 + Period 2 + . . . + Period 12 = FULL YEAR

If you type data in the Company Total cell, breakback allocates the total pro rata according to an initial profile or weighting. The value of the original items held in the detail items determines that profile. For example, if you have a D-Cube with four divisions and a Company Total, with each division having the number 25 entered in it, the formula would allocate 25 percent of any changes in the total to each variable. If you then typed 1000 in the Company Total cell and pressed Enter, the four divisions would receive 25 percent of 1000, or 250 in each division.

The profile need not be a percentage. For example, suppose each division were given an equal initial weighting of 1, then the result would split equally. If you type 1000 in the Company Total cell and press Enter, the result would still be 250 in each division.

The same result could be achieved by giving an initial profile of all zeros. Before the breakback, everything reads zero; after typing a number in the Company Total cell, every item receives an equal allocation.

Profit = Sales - Costs

Initially Sales =60

Costs =40

So Profit = 20

The effect of increasing Profit from 20 to 30 increases Sales by six and decreases Costs by four in direct proportion to their initial values.

The relative size of the initial values determines the percentage change of each variable.

The effect of breakback on formulas containing multiplication is slightly more complex, but again, the pro rata rule applies. For example, if you have the formula

Sales = Units * Price

If Sales are doubled, both Units and Price increase by the same percentage with respect to their original values. In this case, both will increase by the square root of 2.

The effect of breakback on formulas containing division is similar to multiplication. The effect of an increase in the result is to increase the numerator by the same percentage as the denominator. Again, the pro rata rule applies. For example, if you have the formula

%Margin = (Margin / Sales) * 100

If % Margin is increased, Margin goes up by the same percentage as Sales go down. This keeps both variables in proportion to their original values. In fact, if % Margin doubles, then Margin goes up by a factor of the square root of two whereas Sales go down by a factor of the square root of two.

In this last case, it would be better to hold or increase Sales before changing %Margin. The computer lacks the intelligence to know whether an increase in %Margin is best achieved by an increase in Sales, a reduction in Costs, or some mixture of the two.