To calculate an inverse weighted average, follow these steps:

1. Determine the weights: In this case, the weights will be the inverse of the income for each member. To calculate the inverse, you can divide 1 by the income for each member. For example, if one member has an income of $10,000, their weight would be 1/10,000 = 0.0001.
2. Calculate the weighted values: Multiply each item by the weight for the corresponding member. For example, if you have an item worth $100 and the member with an income of $10,000 has a weight of 0.0001, their weighted value for that item would be $100 * 0.0001 = $0.01.
3. Sum the weighted values: Add up all the weighted values for each member to get the total weighted value.
4. Sum the weights: Add up all the weights for each member to get the total weight.
5. Calculate the inverse weighted average: Divide the total weighted value by the total weight. This will give you the inverse weighted average.

For example, let's say you have three members with incomes of $10,000, $20,000, and $30,000, and you want to allocate an item worth $100 among them. The weights would be 0.0001, 0.00005, and 0.000033, respectively. The weighted values for the item would be $0.01, $0.005, and $0.0033, respectively. The total weighted value would be $0.0183, and the total weight would be 0.000183. Dividing the total weighted value by the total weight gives an inverse weighted average of $100.