Public Eavesdropping"She can't be homophobic. She drives a Prius." Resident of a senior housing community, overheard in Sonoma County by Trish Benedict
Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/08/22/DDH11KOI98.DTL#ixzz1VrsQm9lj
The quote actually is related to my own research on environmental ideology (see this). Open up a microeconomics book and you won't find the word "ideology" mentioned in the consumption chapter. Instead, you will see a long discussion of budget sets (what people can afford to buy) and you will see indifference curves (which represent a consumer's willingness to tradeoff one good for another). The author will not tell you where the consumer's preferences come from.
In my "new vision" for micro theory, households differ with respect to their intrinsic ideology. It remains an open question where this ideology comes from. Consumers know their ideology and act upon it. In the case of my work on "green products", those with a liberal ideology are more likely to engage in voluntary restraint and want to purchase the Prius, solar panels, carbon offsets and in general live a "small footprint" lifestyle even if there are not explicit Pigouvian taxes for polluting.
Now, how does this relate to Homophobia? If you are willing to assume that liberals are less likely to be homophobic and if liberals tend to drive the Prius (which they do), then it follows by transitivity that Prius drivers should be pro-gay rights.
Note that driving a Prius doesn't "make you" pro-gay rights, instead a 3rd cause (liberal ideology) drives both behaviors.
This correlation between ideology and Prius ownership would weaken during a time of high gas prices or a time when gas prices are expected to rise. In this case, we would see more people (regardless of ideology) buying fuel efficient vehicles. For the subset of people with extremely long commutes, they will also buy the high MPG vehicle regardless of their politics.