These measures (all based on the five years prior to the focal year) are the total number of portfolio companies a VC invested in; the total funds invested in portfolio firms; the total dollar amount of funds raised; the number (count) of individual funds raised; the number of portfolio firms taken public; and VC age in the focal year (calculated as the IPO year minus the year a VC firm raised its first fund)
这句话里的 the focal year 该如何理解呢，焦点年？