We analyze the success of filtering as a solution to the spam problem when used alone or concurrently with sender pricing, receiver pricing, or both. We find that filtering alone may exacerbate the spam problem in terms of both the total number of spam message sent and the expected number of...

Matching models of the labour market have been of particular interest in macroeconomics where the notion of 'thick-market' externalities can lead to multiple equilibria. This has led to some recent interest in constructing empirical estimates of labor-market matching functions. This paper argues...