We have used a model of magnetic accretion to investigate the accretion flows of magnetic cataclysmic variables ( mCVs ) .
Numerical simulations demonstrate that four types of flow are possible : discs , streams , rings and propellers .
The fundamental observable determining the accretion flow , for a given mass ratio , is the spin-to-orbital period ratio of the system .
If IPs are accreting at their equilibrium spin rates , then for a mass ratio of 0.5 , those with P _ { spin } / P _ { orb } { \small \raisebox { -2.58 pt } { $ \stackrel { \raisebox { -0.86 % pt } { $ \textstyle < $ } } { \sim } $ } } 0.1 will be disc-like , those with 0.1 { \small \raisebox { -2.58 pt } { $ \stackrel { \raisebox { -0.86 pt } { $ \textstyle < $ } } { % \sim } $ } } P _ { spin } / P _ { orb } { \small \raisebox { -2.58 pt } { $ \stackrel { % \raisebox { -0.86 pt } { $ \textstyle < $ } } { \sim } $ } } 0.6 will be stream-like , and those with P _ { spin } / P _ { orb } \sim 0.6 will be ring-like .
The spin to orbital period ratio at which the systems transition between these flow types increases as the mass ratio of the stellar components decreases .

For the first time we present evolutionary tracks of mCVs which allow investigation of how their accretion flow changes with time .
As systems evolve to shorter orbital periods and smaller mass ratios , in order to maintain spin equilibrium , their spin-to-orbital period ratio will generally increase .
As a result , the relative occurrence of ring-like flows will increase , and the occurrence of disc-like flows will decrease , at short orbital periods .
The growing number of systems observed at high spin-to-orbital period ratios with orbital periods below 2 h , and the observational evidence for ring-like accretion in EX Hya , are fully consistent with this picture .