ESDU 80033 gives graphical data for estimating the wing planform contribution to Lv for aircraft having wings of any trapezoidal planform with aspect ratio between 1 and 12, tip chord/root chord ratio between 0 and 1 and sweep-back of the mid-chord line between 0 and 60 degrees. The formulae given apply also to swept forward wings for which case reference is given to theoretical data on the spanwise position of the centre of pressure, which is needed to evaluate the formulae. The method takes account of the effect of wing sweep on a theoretical basis and this is used to establish the zero-sweep contribution empirically from a large number of wind-tunnel test data. Compressibility effects are taken into account up to the Mach number at which aerodynamic characteristics start to change rapidly. A worked example on the use of the data is included.