A market capitalization weighted index representing the smallest 800 companies in the Russell 1000 Index. The average Russell Midcap Index member has a market cap of $8 billion to $10 billion, with a median value of $4 billion to $5 billion. The index is reconstituted annually so that stocks that have outgrown the index can be removed and new entries can be added. Taobiz explains Russell Midcap Index The Russell Midcap Index is a complete subset of both the Russell 1000 and the Russell 3000. Midcap fund managers have few good indexes against which to benchmark their returns, making the Russell Midcap Index a valuable one for institutional portfolio managers. The range of market caps covered in this 800-member index goes from about $1 billion on the low end to roughly $20 billion.