listMarketBook - wrong number of winners?

[Mr Magoo]

The API has some confusing behaviour with horse racing place markets. For example, market 1.122375473 (Font 26th Dec - 12:55 - 2 To Be Placed).

Only one horse actually finished in this race, so naturally only one of the runners has the status 'WINNER'. However, if you call listMarketBook() on the market now, it also reports that numberOfWinners = 1. IMO this is the wrong thing to be reporting, the API should really be reporting numberOfWinners = 2, as it would have done prior to the start of the race.

After all, anyone can check the returned results and spot that only one horse won, but there's no easy way to discover (after the event) that the market was for 2 places. The 2 should be kept.

[Mr Magoo]

There are related problems in the historic data from data.betfair.com. For example, market 1.122355241 was declared as 'Ling 21st Dec - 12:40 4 TBP', and my records of the betting show that it was always a market with 4 winners in, with betting close to 400% as expected.

But, in the historic data, this market is listed as having the title '3 TBP'. This, I suspect, is because there were only three horses that actually finished the race. But Betfair should not be changing the title of the market to match, that's plain wrong and very misleading.

Even the actual website now refers to the closed market as being titled '3 TBP' : https://www.betfair.com/exchange/plu...et/1.122355241

To repeat: before the market closed, this was always a 4 winner market. The betting reflected that. There was no sign pre-race that the event changed the number of winners. But after the market was settled, the historic data has been wrongly changed to label it three places. This is badly wrong because if people analyze the historic betting, they'll get their calculations wrong.

[Mr Magoo]

Betfair have confirmed that this is a known problem, it's due to the way they settle markets when there are fewer finishers than the number of places in the market. As a result, data in the historical files might have the wrong market names.