ESRC Data Archive Bulletin:
An Overview of the Building Society Mortgage Survey

The principal source of detailed official statistics on the private sector housing market is that of the 5% Sample Survey of Building Society Mortgages (Archive study number 33191). This survey is carried out by the Department of the Environment in conjunction with the Building Societies Association and dates from the end of 1965. At different the questionnaire upon which the survey is based has been subject to revision. One such example of a mainline revision was in 1982 when the analysis of the previous tenure of borrowers was extended to identify sitting tenants. An example of a more recent major revision was in April 1992. The survey was broadened to obtain information not only on first advances but also remortgages and further advances. At the same stage the survey coverage was extended to encompass not only building societies plus Abbey National plc but also the returns of other mortgage loan institutions such as banks, household mortgage companies and insurance companies. In short, the survey has been extended to include members of the Council of Mortgage Lenders. As yet results for this broadened coverage have not been published.

A core feature of the survey in the past and one which will remain for the foreseeable future is the 5% sample survey of building society mortgage completions. For the purposes of the survey, building societies are divided into four strata. The stratum to which they are allocated is determined by their volume of total assets. The first stratum consists of large societies. This grouping is requested to complete questionnaires on a sample of 5% of their new mortgages advances. In the second stratum every second society is chosen and requested to complete questionnaires on 10% of their mortgages. In the third stratum every fourth society is chosen with the questionnaire coverage, in this instance, 25%. The fourth stratum which is made up of the smallest societies is excluded from the analysis. Only one of the two indigenous Northern Ireland building societies features in the survey. The Londonderry Provident Building Society with an asset base in 1991 of 5 million falls into the fourth stratum and is not covered. In contrast the Belfast based Progressive Building Society, with an asset base in 1991 of 256.3 million, is allocated to the second stratum and is one of those chosen to complete monthly questionnaires on 10% of its mortgage advances. In actuality, however, the Progressive returns on average 10 questionnaires per month which adds up to a 5% coverage of its mortgage advances.

Although the survey coverage is supposed to be 5% the actual outturn is much closer to 3.5% with this representing a coverage of approximately 8,000 mortgages per quarter. One reason that the sample proportion is consistently less than 5% is a consequence of the exclusion of small societies from the analysis and under returns by some societies, as in the case of the Progressive. This, however, accounts for only a small part of the shortfall. Another reason put forward is that advances included in the analysis of the sample survey are restricted to those granted for the purchase of dwellings for occupation, whereas the estimated totals include all advances for the purchase of dwellings (Evans, 1975). In addition, it is argued that there appears to be a shortfall in the combined requisite number of questionnaire returns after the occurrence of transfers of engagements and/or mergers between societies. This latter point may be viewed as particularly pertinent given the rapid decline in building society numbers over the last number of years. For example, in 1991 alone there were 8 transfers of engagements and by the end of 1991 there were only 91 registered members of the Building Societies Association in operation. This compares with 255 ten years ago.

The specific object of the survey is to collect all the particulars of the "mortgage transaction". In consequence the information is collated under three broad headings: the mortgage advance; the dwelling; and the main applicant. A total of some 116 regular computer tabulations are now produced from the survey data for each quarter and calendar year, although recently, prior to revisions, a total of some 300 tables were produced. It is argued that the list of regular tabulations is continually under review. Consequently as demand arises new tabulations can be provided with the opportunity to produce them retrospectively.

The majority of both the key national and regional results from the survey are published by the Department of the Environment and the Council of Mortgage Lenders.

In the case of the Department of the Environment the principal quarterly results from the survey are published in the Department of Environment's Housing and Construction Statistics. These figures are, in addition, released by press notice usually within two months after the end of the quarter to which they refer. Other results from the survey are published annually in Housing and Construction Statistics in the form of supplementary tables.[1]

Broadly similar tabular information is also provided by the Council of Mortgage Lenders in Housing Finance. This is a quarterly journal on the mortgage market and provides features on the housing and mortgage market plus, in the spring issue, 25 tables "covering all aspects of housing and mortgage market activity". The latest edition, Housing Finance, No.14, May 1992 provides an analysis of building society mortgage lending in 1991.

Some of the figures published in the above sources are also available elsewhere, for example in Government publications such as Social Trends. Furthermore, the data obtained from the survey is also made available to the ESRC Data archive at Essex.

So far the concentration in this overview has been on building societies. Building societies now, however, account for only 75% of the funds available for mortgage finance. To accommodate this fact the above noted publications have introduced tabular material on mortgage advances from other loan institutions. In Housing and Construction Statistics, for example, material has been incorporated on mortgage advances and dwelling prices for both banks and insurance companies. The information provided is obtained respectively from the Bank of England and the British Insurance Association sample survey. For the future, however, the revised extended survey which covers mortgage lenders will eliminate the problem of the survey being constrained simply to building societies.

In terms of the regional emphasis of the mortgage survey the majority of variables are analysed by region and include information specifically on Northern Ireland. Indeed across Housing and Construction Statistics and Housing Finance there is a wide range of published information already available for Northern Ireland. Information is provided both in single form and in terms of variables analysed in conjunction with others. Examples of available single form information include the regional distribution of: loans; housing stock; house completions; mortgaged dwellings; age of dwelling; type of dwelling; income of borrowers; previous tenure of borrower; age of first time buyer; sex of borrower; average dwelling price; deposit paid and average advance. For the most part the cross tabular information presented tends to concentrate upon regional loan distribution, dwelling type and borrower status vis a vis the other variables listed above.

One problem which invariably occurs, particularly when national data is broken down into its constituent regional parts, is whether the same size is large enough to yield reliable results. Pannell (1992) states that, while for the most part the sample size is large enough to yield meaningful results, caution at times needs to be employed in interpreting the figures with this particularly the case in respect of some of the figures for Northern Ireland. Approximate coefficients of variation are reported in Housing and Construction Statistics for average dwelling prices, advances and incomes. It is clear from these values that the likely sampling error both year-on-year and quarter-on-quarter is much higher in Northern Ireland than in other regions of the United kingdom. On average for Northern Ireland the maximum likely sample error in year-on-year (quarter-on-quarter) percentage charges in the various series is 5.4 (12.4). Computing the average series error for each of other United Kingdom regions and then taking the average regional score yields comparable values of 2.9 (6.5). This reinforces the point that caution must be exercised in interpreting figures for Northern Ireland.

Finally it should be noted that the revised and extended mortgage survey as it currently stands omits some of the main players in the mortgage market in Northern Ireland. The most notable omissions are the Northern Bank and the Ulster Bank. The explanation for their omission rests with the fact that they are not members of the Council for Mortgage Lenders. The Department of the Environment is, however, not constrained to sample members of the Council of Mortgage Lenders only and consequently it should be a relatively easy matter to accommodate these institutions in the sample survey. Irrespective of the ease or otherwise of including these banks in the sample, it is nevertheless important that they should be, given their role in the mortgage market in Northern Ireland and the fact that neither the London and Scottish clearing banks nor the home loan companies are represented in Northern Ireland.

In summary it can be said that a number of problems arise vis-`a-vis the Northern Ireland dimension of the Mortgage Survey. Most notable amongst these are the sample size for certain variables, the under-return by the only Northern Ireland-based society included in the sample and the limited sample coverage of the revised survey. It should nevertheless also be evident that the survey offers a broad spectrum of regional specific data on the various facets of the mortgage transaction.

References

Evans, A.W., (1975), CSO Studies in Official Statistics, No.26.
Pannell, B., (1992), "Survey of Mortgage Lending 1991", Housing Finance, No.14.

Note:
[1]. Tables not available in these publications can be obtained directly from the department of the Environment although a charge is levied for non-academic users.