There are many challenges developers face when attempting to reliably extract data from the Web. One of these challenges is the resilience of the extraction system to changes in the web pages information is being extracted from. This article compares the resilience of information extraction systems that use position based extraction with an ontology based extraction system and a system that combines position based extraction with ontology based extraction. The findings demonstrate the advantages of using a system that combines multiple extraction techniques, especially in environments where web sites change frequently and where data collection is conducted over an extended period of time.