Theoretically, the odds for Red and Black are even. In a 1000 games, you should expect that Red and Black appear with the same frequency, that is 500 times each. This goes also for other even money bets like Even / Odd and so on. However, things are a little different in real life. In fact, it is rather improbable that Red appears exactly 500 times in a 1000 games. It will appear more or less often than 500 times, and this deviation is called Ecart. This Ecart can amount to more than 10 % (563 times Red/ 437 times Black). This deviation from the ideal odds is called tension.

Several game systems take these deviations into account. Example: If Black has appeared less frequently than Red in previous games, it is all the more likely that Black will appear more often than Red in the following games. The betting system will focus on Black according to a certain deviation from the ideal odds of the two colours.

The following table is intended for better illustration of this game system. It is recommended to bet on Red after Black has appeared for the fifth time. Additionally, a progression is used.

Red	Black	Stake	Balance
	x
x	x
	x
	x
	x
	x
	x	signal for bet on Red	+10
	x	20	-30
	x	40	-70
x		80	+10
	x	10	0
x		20	+10
x		10	+20
x		10	+30
x		10	+40
x		10	+50
x		10	+60

Experiments have shown that the number of games played has a distinctive influence on the odds. The higher the number of games played, the more even the odds become. The effect of Zero has not been taken into account in this table.

The shorter the game series you observe, the higher becomes the deviation and therefore the odds for the colour which appeared less often beome more favourable. If Red is played 15 times in 20 games, the odds for Black will get better and better in the following games.