Using procurement for political ends gives you worse prices.

Over 20 years ago, some middling economists (cite) estimated that the Small Business Set-Aside program reduced Forest Service Timber prices by 15%.  By limiting the potential pool of available bidders to only smaller lumber mills, you get less competition and worse prices.

Now San Francisco is re-learning that lesson.  In 2016, it refused to do business with companies headquartered in states that don't share San Francisco's values. As a result, project costs increased 20 percent. 

Two forces are at work:  

• Short-run reduction in competition:  just as mergers which eliminate competition raise price, so too does limiting the number of bidders.  

NOTE:  a reduction in competition in a selling auction (high bid wins, e.g., timber), price goes down; in a procurement auction (low bid wins, e.g., city services) price goes up.  

• Long-run decline in bidder quality:  winning bidders must outbid the losers, so if losing bidders from states that share San Francisco's values--like unionization--have higher costs, they are easier to outbid, so price goes up.

REASON, "Great Moments in Unintended Consequences"