The targeted growth of variable generation capacity in many power systems has led to concern that future systems may have insufficient flexibility to meet ramps in variable generation (VG) production and system demand. This paper introduces a high-level flexibility assessment methodology for use by those involved in planning, and with little experience of the integration of large quantities of variable generation. This is proposed as a first step in assessing the future needs of a system. Comparison is drawn between the proposed high-level flexibility assessment and a more detailed flexibility assessment. The insufficient ramp resource expectation (IRRE) highlights those time horizons in which the system may have insufficient flexibility to meet changes in the net load. The methodology is demonstrated on a test system from which high-level conclusions may be drawn. A number of other insights are also offered by the proposed methodology, including the distributions of the size of the deficit, and surplus, of ramping capability.