We study entry and bidding in procurement auctions where contracts are awarded to the bid closest to a trimmed average bid. These auctions, common in public procurement, create incentives to coordinate bids to manipulate the bid distribution. We present statistical tests to detect coordinated entry and bidding choices. The tests perform well in a validation dataset where a court case makes coordination observable. We use the tests to detect coordination in a larger dataset where it is suspected, but not known. The results are used to interpret a major market shakeout following a switch to first price auctions. (JEL D44, D47, H57, R42)

In particular, I use the so called "Schede" dataset which consists of 11 schede (i.e., forms) compiled by the PAs procuring public works during the different phases of the procurement process. The IE sample, instead, comes from the database on road construction works of a private company, http://www.telemat.it/. This is a major information entrepreneur (IE) and its main activity is selling information about public contracts to construction firms.

This paper shows how in Medicare Part D insurers' gaming of the subsidy paid to low-income enrollees distorts premiums and raises the program cost. Using plan-level data from the first five years of the program, I find multiple instances of pricing strategy distortions for the largest insurers. Instrumental variable estimates indicate that the changes in a concentration index measuring the manipulability of the subsidy can explain a large share of the premium growth observed between 2006 and 2011. Removing this distortion could reduce the cost of the program without worsening consumer welfare.(JEL G22, H51, I13, I18)