Table 1

Effect of concurvity on confidence interval coverage*. Results of the simulation study using asymptotic (standard method in gam software) and conditional bootstrap. True coefficient = 0.001

Concurvity	Coverage*
Concurvity	Asymptotic	Bootstrap
*Percentage of replicates that include the true value of the coefficient within the 95% CI of the true coefficient 0.001. Nominal coverage is 0.95. †Degree of concurvity for our real data.
0.045	0.962	0.964
0.103	0.946	0.946
0.149	0.950	0.946
0.199	0.921	0.938
0.251	0.921	0.951
0.286†	0.905	0.952
0.329	0.907	0.961
0.399	0.879	0.955
0.451	0.863	0.940
0.498	0.861	0.946
0.533	0.862	0.940
0.632	0.801	0.950