Assorted links

by on March 23, 2009 at 11:07 am in Web/Tech | Permalink

1. Blog of Italian economists, sometimes in English.

2. Do recommender systems produce on-line monoculture?

3. Atonal credit swaps.

4. Against cul-de-sacs.

5. Steven Cheung update.

David Hecht March 23, 2009 at 11:53 am

I certainly won’t claim I fully understand the analysis of “online monoculture”, but ISTM that the models described fail to differentiate between recommender systems for products where there really is a hierarchy of value (e.g., computers, consumer electronics) and those where there isn’t one (e.g., books, music).

If online recommender systems say that Vendor X’s newest plasma display is the best value you can get, and this causes a clumping of choices by consumers, I don’t really see a problem. After all, that generally means that all the other plasma display vendors will have to work harder to earn my dollar the next go-round…and there will be another clump, different than the first one.

Cyrus March 23, 2009 at 1:05 pm

From #2: So I wrote a program that does basically what they do in their paper and tweaked it to highlight this result.

But a priori, we don’t know how a particular recommendation algorithm will impact a particular media market.

Doug March 23, 2009 at 2:51 pm

Here here. Finally some common sense from planners.

ogmb March 23, 2009 at 3:15 pm

David:

The point of recommender systems is not so much to snoop out the power drill that works best for everybody but to match each customer with the product that best fills their individual needs. In addition recommender systems are employed in very large product spaces where each individual customer can only survey a small fraction of the space but (it is hoped) the population of users can illuminate the whole space. There are two potential problems with recommender systems: first, signaling a preferred choice leads to increasing returns for that choice. Items that are more visible might attract more attention simply because they’re more visible, not because they’re better than other (new or insufficiently visible) alternatives — the product space never gets sufficiently illuminated and product-customer matching is suboptimal. And second, in some markets monoculture is detrimental even if the “mono” choice is in fact the best alternative, since lack of diversity has a negative effect on product development.

That said, these two little simulations don’t come near establishing that monoculture is in fact a serious problem in online markets. They only shows how it could occur. So there is as of now no reason to distrust our gut instincts based on their findings.

ogmb March 23, 2009 at 4:27 pm

tom:

I’m not aware of a specific claim that recommender systems promote diversity, so let me try to formulate my own: Recommender systems do not promote diversity per se, online markets do (by increasing the accessible product space over brick-and-mortar stores). Recommender systems concentrate the product space to facilitate choice, so if the product space is invariant between online store and offline store, it is possible that concentration of sales goes up through recommender systems, but this fails to take into account the purpose of the recommender system and its effect if product space differ between online and offline store. I agree that it is up to the originator of such a claim to validate it empirically, but I believe your simulation misses out on the core driver of diversity of a recommender system: that it allows the customer to survey a much larger product space than an offline store.

allen dalton March 23, 2009 at 9:26 pm

There is a simple solution regarding the costs of maintaining cul-de-sacs. Privatize the roads. I live in a small cul-de-sac development – seven houses. We went to the county and changed our street to a private road; that allowed us to gate the entrance and we use homeowner association fees to maintain it. The cul-de-sac and gate meant that our children were able to safely play in the street, riding bikes, playing whiffle ball, street hockey, etc. while they were growing up. And our new neighbors – with young triplets – will enjoy the same safety. Developers could certainly offer this alternative to Virginia counties, couldn’t they? However, it appears from the story that the cost argument may just be a cover for a collectivist desire to minimize privacy and force “community” on homeowners.

Douglas Knight March 24, 2009 at 12:31 am

allen dalton:
did you read the article? VA is privatizing the roads. That’s all the law does: VA won’t maintain new cul de sacs.

chriswnw March 24, 2009 at 7:00 pm

Also, by “subdivision”, I specifically meant “superblock”. I don’t think that every private community or development should be a thoroughfare, but that it should be possible to get through every superblock without using the arterials.

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