Bellwether seats: a reader email s

The definition of a 'bellwether seat' is always strictly retrospective, and has no predictive value. When I was born, in 1964, the bellwether seat _par excellence_ was Corio. That retrospective (from 1964) fact had no predictive value, as is now confirmed retrospectively (from 2007). 

When I reached voting age, in 1982, the bellwether seat _par excellence_ was Denison. That retrospective (from 1982) fact had no predictive value, as is now confirmed retrospectively (from 2007). 

Seats change. Seats which used to be safe become marginal, like Richmond; seats which used to be marginal become safe, like Aston.