Rhenania, a German direct mail-order company, turned its catalog mailing practices around within one year and consequently moved up in market position from number 5 to number 2.  A dynamic multilevel modeling (DMLM) approach uses elasticities to determine the optimal frequency of catalog mailings, a customer-segmentation approach allows for optimization of mailings, and a recency, frequency monetary-value (RFM) segmentation in combination with a chi-square automatic interaction detection (CHAID) algorithm determines when customers should receive a reactivation package-as opposed to a catalog-to optimize mailing efficiency further.  The DMLM approach was so effective that Rhenania acquired two competitors (one a subdivision of Springer Verlag).