it does not introduce respondent bias, which is commonly found in primary research; it can identify and map out the entire scientific community for a disease state; and it has greater compliance with state and federal regulations; because physician prescribing patterns are not used to create the social network. Alternatives to segmenting physicians purely on the basis of prescribing do exist, and marketers can call upon strategic partners who specialize in delineating which characteristics of true opinion leadership, a physician does or does not possess. Such analyses can help guide marketers in how to optimize KOL engagements as bona fide advisors to a brand, and can help shape clinical development and clinical data publication plans for instance, ultimately advancing patient care. Colleagues Physicians acquire information through informal contacts with their colleagues, including social events, professional affiliations, common hospital affiliations, and common medical school affiliations. Some pharmaceutical companies identify influential colleagues through commercially available prescription writing and patient level data. Doctor dinner meetings are an effective way for physicians to acquire educational information from respected peers and to influence the so-called "no-see" physicians - those that are reluctant to engage directly with pharmaceutical reps through detailing but may come to a dinner program where a local or national expert is talking. These meetings are sponsored by some pharmaceutical companies. Journal articles and technical documentation Recent legal cases and US congressional hearings have provided access to pharmaceutical industry documents revealing new marketing strategies for drugs. Activities once considered independent of promotional intent, including continuing medical education and medical research, are used, including paying to publish articles about promoted drugs for the medical literature, and alleged suppression of unfavorable study results. Private and public insurers Public and private insurers affect the writing of prescriptions by physicians through formularies that restrict the number and types of drugs that the insurer will cover. Not only can the insurer affect drug sales by including or excluding a particular drug from a formulary, they can affect sales by tiering, or placing bureaucratic hurdles to prescribing certain drugs. In January 2006, the United States instituted a new public prescription drug plan through its Medicare program. Known as Medicare Part D, this program engages private insurers to negotiate with pharmaceutical companies for the placement of drugs on tiered formularies. To consumers Only two countries as of 2008 allow direct to consumer advertising (DTCA): the United States and New Zealand.