size analysis where possible. The survey panels therefore replicate the actual economy in miniature. A weighting system is also incorporated into the survey database that weights each response by company size and the relative importance of the sector in which that company operates. Particular effort is made to achieve monthly survey response rates of around 80%, ensuring that an accurate picture of business conditions is recorded over time. Data are collected in the second half of each month via mail, email, web, fax and phone. Questionnaires A key feature of the PMI surveys is that they ask only for factual information. They are not surveys of opinions, intentions or expectations and the data therefore represent the closest one can get to “hard data” without asking for actual figures from companies. Questions asked relate to key variables such as output, new orders, prices and employment. Questions take the form of up/down/same replies. For example, “Is your company’s output higher, the same or lower than one month ago?” Respondents are asked to take expected seasonal influences into account when considering their replies. For each main survey question, respondents are asked to provide a reason for any change on the previous month, if known. This assists not only the understanding of variable movement but also in the seasonal process when X12 cannot be used. Seasonal adjustment The seasonal adjustment of PMI survey data is usually calculated using the X12 statistical programme of adjustment, as used by governmental statistical bodies in many developed countries. However, the X12 programme only produces satisfactory data if five years' historical data are available. In the absence of such a history of data, the PMI survey data are seasonally adjusted using an alternative method (see next paragraph), developed by Markit Economics. This method was initially designed to provide analysts with a guide to the underlying trend in the survey data and should be recognized as a second-best approach to X12. However, past experience in other countries suggests that Markit’s method of seasonal adjustment goes beyond this initial purpose and in fact in many cases outperforms X12 as a guide to comparable official data. Markit's method involves using reasons cited by responding survey panel member companies for changes in variables, which are then used to ascertain whether a reported increase or decrease in each variable reflects an underlying change in economic conditions or simply a seasonal variation. Seasonal variations may