The main problem is that knowledge resides in people's heads. It is what people know. It is difficult to get access to it, or to control it, or to add to it. Data is the sea of facts which surrounds us, much of it low quality, irrelevant or redundant. From this sea of data we have to select and combine relevant bits to create information - that which 'informs' people.
Statisticians are very good at turning data into information.
People transform this information into knowledge through a process of learning and understanding. Clearly knowledge is a personal thing, and thus human capital or intellectual assets become a high priority for any organisation. For today's organisations, knowledge management is a key strategic issue. The study of knowledge is not new. Philosophers have been addressing knowledge for thousands of years.