  We study the efficiency of sequential multiunit auctions with two-buyers and
complete information. For general valuation functions, we show that the price
of anarchy is exactly $1/T$ for auctions with $T$ items for sale. For concave
valuation functions, we show that the price of anarchy is bounded below by
$1-1/e\simeq 0.632$. This bound is asymptotically tight as the number of items
sold tends to infinity.
