Final answer:
The algorithm from 2009 may not have worked anymore when it was applied again in 2013 due to technological advancements, changes in data, and shifts in user behavior.
Step-by-step explanation:
The algorithm from 2009 may not have worked anymore when it was applied again in 2013 due to several reasons:
- Technological advancements: Technology evolves rapidly, and algorithms created in 2009 may not have been designed to handle new technologies or changes in software or hardware.
- Data changes: The algorithm may have relied on certain data or assumptions that were no longer valid in 2013. Changes in data sources, data collection methods, or data availability could have impacted the algorithm's effectiveness.
- User behavior: User behavior and preferences change over time. The algorithm might have been optimized for a particular user base or context in 2009, but those factors could have shifted by 2013.