why does the model always break in backtesting around mid-2010 ?

Question

I am backtesting a few ideas and they always seem to fall apart in 2010.  Was this a change in legislation ?

Answer 1

There was a change to starting stalls numbering on right handed tracks at the start of the Flat season in 2011, but apart from that, no....

Answer 2

Wasn't there also a change to the class structure of British horse races around that time?

Comments

Yes I think you're right - also lots of shake ups to the fixture system have been in progress over the last 5 years in general, as bookies seek to increase the amount of handicaps and reduce predictability in horseracing...