Multi-unit auctions, like those for FCC spectrum and Treasury debt, can be inefficient due to large bidders reducing demand to pay less. This leads to smaller bidders sometimes winning with lower values. Different auction settings show this inefficiency, and the ranking of auction types can be unclear. A Vickrey auction can avoid this issue, implemented with an ascending-bid design. Bidding behavior in FCC spectrum auctions highlights the problem of demand reduction and inefficiency.