Ompensation Programs: Seniority Pay Systems vs Performance Pay Systems

During the early part of 1900s, unions became a driving force in labor throughout the United States and with that so did seniority systems as a way to levy out annual pay raises. Now as the economics of the United States have expanded into global markets and the industries have shifted from manufacturing to service related industries; more companies are looking towards different ways to compensate their employees. In order to achieve strategic business goals and get employees to perform at higher levels; employers are looking towards changing the way that they compensate their employees. They are looking towards a pay system that awards compensation based on performance and merit, rather than strictly seniority pay structure.
Whatas the history behind seniority pay systems? (briefly)
How have employee pay systems changed over the last 100 years and what are the current trends in salary and compensation systems?
What are the emerging trends in the United States? Globally?
How does the United States compensation system differ from Europe? Asia?
Look at emerging trends in both the United States and globally.