Table 2.

The response rates

	General response rate	Final sample response rate
Admission	n = 178 of 320 (56%)	n = 31 of 54 (57%)
First year	n = 178 of 320 (56%)	n = 32 of 54 (59%)
Second year	n = 129 of 280 (46%)	n = 22 of 54 (41%)
Third year	n = 127 of 302 (42%)	n = 23 of 54 (43%)
Fourth year	n = 121 of 288 (42%)	n = 21 of 54 (39%)
Fifth year	n = 58 of 271 (21%)	n = 10 of 54 (19%)
Sixth year	n = 138 of 240 (57%)	n = 19 of 54 (35%)