Income Elasticity & PED

Revision.

Income Elasticity

https://www.youtube.com/watch?v=a6AHaqlm7J4&feature=youtube_gdata_player

Price Elasticity
http://www.youtube.com/watch?v=M5PkDjO998E&feature=youtube_gdata_player

Theres another on the Economics page.
you may need https rather than http to link to youtube.