An informal survey conducted by the National Trust raises troubling questions about property museums: whether the facility is safely preserved and whether the museum facilitates the public's understanding of history, namely, whether the site itself lacks a sense of historicity. Staff and maintenance are dependent upon unstable funding sources; 65% of these sites surveyed have no professional staff whatsoever. The boards responsible for these properties tend to be so preoccupied with maintaining the structural integrity of the facility that they do not think through the problem of what they are preserving.