From a preprint study posted on the Cornell University open-access archive arXiv in October that was conducted by researchers at more than a dozen European universities.

A group of forty-eight people tossed coins of forty-six different currencies and obtained a total of 350,757 coin flips. We found strong empirical confirmation that when a person flips a coin, it tends to land on the same side as it started on. The magnitude of the observed bias can be illustrated using a betting scenario. If you bet a dollar on the outcome of a coin toss (i.e., paying one dollar to enter and winning either zero or two dollars depending on the outcome) and repeat the bet one thousand times, knowing the starting position of the coin toss would earn you nineteen dollars on average. This is more than a casino’s advantage in six-deck blackjack against an optimal-strategy player, in which the casino would make five dollars on a comparable bet. These considerations lead us to suggest that when coin flips are used for high-stakes decision-making, the starting position of the coin should be concealed. Future work may attempt to verify whether wobbly tossers show a more pronounced same-side bias than stable tossers. The effort required to test this more detailed hypothesis appears to be excessive.