# Backing and Laying based on the change in WOM

### Description

Attention! These triggers will only work with MF Pro Version 8.7.8.3 or later.

The Weight of Money (WOM) shows how much of the money currently offered on a given selection is one the back or lay side (Back WOM and Lay WOM respectively). This is not to be confused with the pressure of traded money, as WOM operates with unmatched amounts, i.e. the amounts displayed beneath the price figures on betting buttons.

Here is what Back WOM and Lay WOM mean in practice:

Although the idea that WOM can help to predict the price movement is losing its positions among the traders, it still has the same logical background. If there is more money on the back side, it means layers are betting more actively, and so the price is likely to rise in a short while. The opposite is when there is more money on the lay side, which means the price is likely to drop.

The mathematical representation of WOM is very simple:

`Back WOM = back_volume/(back_volume + lay_volume)`

`Lay WOM = lay_volume/(back_volume + lay_volume)`

Where back_volume and lay_volume are the total amounts of money offered on the back and lay side respectively.

Based on the above, two simple WOM strategies can be formulated:

For high-liquidity markets, such as UK races:

1. Starting from 5 minutes before the off, remember the difference between the back and lay WOMs of each selection. If the difference is less than 0, it means there was more Lay money on a particular selection, otherwise there was more back money. We are looking for a difference no less than 20% (so either 20% or -20%), otherwise the selection does not qualify. Let's call this difference the old WOM.
2. Once the ratio of back and lay WOM reverses for any of the selections, e.g. it used to be 70% vs 30% and is now 25% vs 75%, place a bet on that selection. To decide which type of bet to place, deduct the current Lay WOM from the current Back WOM.
LAY if the difference is at least 20% and the old WOM was at least -20% (could be -30%, -40% etc.)
or
BACK if the difference is at least -20% (-30%, -40%, etc.) and the old WOM was at least 20%.
3. Green up for the predefined number of ticks of profit.
4. There is also a trigger for closing all open positions by trading out right before the start of the event. You can turn this trigger off if you like.

For low-liquidity markets, such as Australian races:

1. Starting from 5 minutes before the off, remember the difference between the back and lay WOMs of each selection.
2. Once the Back WOM drops at least 20%, back that selection.
3. Green up for the predefined number of ticks of profit.
4. There is also a trigger for closing all open positions by trading out right before the start of the event. You can turn this trigger off if you like.

### Triggers

Download the trigger example for high-liquidity markets.

Download the trigger example for low-liquidity markets.

You can adjust the trigger settings using the following constants:

 bet_size Size of bet wom_prc Min. WOM advantage, percentage starting_wom Max. starting back WOM, percentage (for low liquidity only) greenup_tcks Green-up ticks start_mins When to remember the initial WOM, minutes before the off stop_mins When to stop betting, minutes before the off close_mins When to trade out all bets, minutes before the off min_sel_vlm Minimum selection volume%

Set the program to start monitoring events at a time that is not less than `start_mins`.

### How it works

The triggers will wait for a qualifying selection and either lay or back on it as soon as there is a notable change in the balance of back and lay volumes.

Later it will try to green up.

Here is an example for a low-liquidity market:

Note: this strategy will be more reliable if you let the triggers take into account the whole range of back and lay offers, not just the best three. Turn on the setting "Download all price offers" in General Options to allow this to happen.

Please keep in mind that in low-liquidity markets the volume of offers will likely be on the back side (there will be more lay bets than back bets on offer).

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