Create categories/types of complaints, such as:
- Level 1 - Minor issue (e.g., perhaps documentation error such as on an invoice or packing slip) that only requires correction
- Level 2 - Moderate issue that requires fixing and an investigation (e.g., wrong quantify shipped)
- Level 3 - Major issue that requires returning product and shipping replacement, and in-depth investigation (e.g., a product defect)
For each level create an estimate the organization is comfortable using. You can the count # of each type and compute total.
Remember the accuracy isn't as critical as the trend.