The book value growth rate for a stock is a measure of how the stock�s book value per share (BVPS) has grown over the last five years. Book value growth is one of the five growth factors used to calculate the Morningstar Style Box. For portfolios, this data point is the share-weighted collective book value growth for all stocks in the current portfolio. (The share-weighted average is more accurate than an asset-weighted average for this type of calculation.)