why do betfair and smarkets shadow each other's odds?

[jobbo]

I don't know if it's applicable to other sports, but for pga golf tournament outrights, betfair almost always has odds just one gradation inside of smarkets, on both sides of the spread.

for example:

if smarkets' spread is:

mcilroy 9.6 - 12

betfair's will be

mcilroy 9.8 - 11.5

even when smarkets spread is something like 20 - 80 betfair's will often be 21 - 75.

i have often seen betfair's odds trail smarkets, so i wonder if betfair themselves use a program to always guarantee they offer better?

(i also feel like i have occasionally seen smarkets trail betfair to offer a spread just outside, but that seems really odd, so maybe i have imagined it?)

can anyone illuminate me?

thanks

[Euler]

Smarkets seed and trade their own markets.

Lots of people take their odds from Betfair and they price to their own margin or to mimic the odds.