compensation of all of our active employees as of December 31, 2020 (the “Determination Date”); (2) ranking the annual total compensation of all employees (except our Chief Executive Officer) from lowest to highest (which comprised a total of 12,260 employees); and (3) selecting the employee who ranked as the median (6,130 on the list of 12,260). We included all of our full-time and part-time employees as of the Determination Date and annualized the total compensation for those full-time and part-time employees who were employed by us for less than one year as of the Determination Date. We applied applicable foreign exchange rates, relative to the U.S. dollar, for our non-U.S. employees. Total annual compensation for each employee, other than the CEO, includes each element of compensation listed in the Summary Compensation Table below, with the exception of employer contributions to any 401(k) or similar qualified, defined contribution plan, and shares granted but not vested, based upon our Company’s payroll records. For ease of administration, bonus dollars for all employees, except the CEO, reflect actual bonus compensation paid in 2020 but earned in 2019. However, as required for the Summary Compensation Table, the bonus dollars for the CEO reflect bonus dollars and associated stock grants earned in 2020 and paid in February 2021.
Annual Incentive Compensation. Our Performance Bonus Plan provides for the contribution of a fixed percentage of pre-bonus operating profit to each of a number of bonus pools, based upon the pre-bonus ROI of each plant, region, and division (each of which is referred to as a “Business Unit”), as well as a separate Corporate Business Unit bonus pool. Combined, these bonus pools are the source for our Company’s aggregate bonus awards.
ROI is determined based upon the Business Unit's pre-bonus operating profit, less income taxes, divided by the average investment of the Business Unit. Average investment is defined as the average of inventory, plus accounts receivable, plus net property, plant and equipment, plus intangibles, less accumulated amortization and less accounts payable.
At the beginning of each year, each Named Executive is allocated a fixed percentage of the bonus pool of his or her respective Business Unit. The amount of an employee's percentage of his or her bonus pool is generally reflective of that person's relative degree of responsibility for the operations and results of that Business Unit, as well as his or her performance and tenure with the Company. If the Business Unit generates profits which result in a bonus pool, the participant receives the allocated percentage as a performance bonus. The dollar amount of that pool is based upon the Business Unit’s aggregate ROI. As ROI increases, a higher percentage of pre-bonus operating profit is contributed to the pool.
For the Corporate Business Unit, the minimum contribution percentage of 4.87% of pre-bonus operating profit occurs at the lowest level of ROI, which is 6.00%. The maximum contribution percentage of 10.47% occurs at an ROI of 25.50% and higher. In general, for every hundred basis point improvement in ROI, the Company contributes an approximate, additional 28 basis points of pre-bonus operating profit to the Corporate Business Unit bonus pool. Three of our Named Executives participated in the Corporate Business Unit bonus pool in 2020.
For 2020, we achieved an overall ROI of 19.83%. This resulted in a gross contribution of $36,605,227 to the Corporate Business Unit bonus pool, which equaled 8.42% of pre-