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Mean fibre diameter is a measurement in micrometres (microns) of the average diameter of wool fibres in a sale lot. Fibre diameter is responsible for 70-80 per cent of the greasy wool price over the long term.

Fine and superfine wool production has increased as a percentage of the Australian wool clip. Australia dominates the supply of fine wool to the international trade, accounting for over 90 per cent of global production of Merino wool of 19.5 micron and finer.

Global demand for finer wool has increased. Manufacturers and processors must source more fine wool to satisfy the global consumers' demand for lightweight garments with next-to-skin comfort, particularly in women's wear.

Micron premiums

The chart below shows the relationship between micron and price. The finer the wool, the higher the price received, with the micron premium increasing as fibre diameter reduces.


Between 17.0 and 20.0 microns, there is over 100 cents difference for each full micron. This falls to less than 50 cents between 21.0 and 22.0 microns. Finer than 17.0 microns, the premium for each micron can be 200 to 400 cents. Lower styles and lower strength types tend to display a much flatter micron/price curve.

Graph of the relationship between micron and price.

Fine wool trends

After peaking in 2000-2001 and the 2002-2003 season, fine wool prices fell away before until November 2003. A brief rebound followed before continuing to drift lower in late 2005. The market then recorded solid increases until prices eased  in mid 2007 only to make solid gains to mid 2008. At this point pieces again fell dramatically, recovering ground from the end of 2009.

Stylish wools have generally underperformed. Only the very best Spinner's styles attract any sort of premium over the lower styled types.

Graph of price trends for fine wool.

Medium wool trends

Medium and broader microns followed the pattern of the finer microns, with prices well below their peak in season 2002-2003. Rises in mid to late 2007 gave way to a slight easing due in part to a decline in the yields and strength (Nkt) of the wools available. 28 micron wool continued to trend sideways, 'lowest common denominator" preparation being the greatest influence on price.

Graph of price trends for medium wool.

The next chart displays micron differentials over time, comparing the quarterly averages for the 21 and 23 Northern and Southern Region Micron Price Guides for the last eight years with 21 micron (x-axis).

The premium for 19 micron wool has a range of approximately 150 cents, with this figure falling around 50 cents since October 2008.

The 23 micron wools increased their margin compared to the 21 micron axis, mainly due to increased demand for mid-micron Merino fleece wool.

Graph of price trends for fine wool.

Wool diameter management tips

The most important decision for woolgrowers with respect to the price received for wool, is the fibre diameter produced. This decision should be based first and foremost on market requirements in the medium to long term.

Failing this, long term historical price relativities are a better guide than recent, short term price margins.

Breeding is the critical determinant of fibre diameter. While environment plays some role in determining the type of sheep run, fine wool sheep are successfully run in pastoral areas and do not necessarily cut less wool.

Compare several ram sources to before changing bloodlines. Review wether trial and sire evaluation information to identify the most productive sheep.

Variation in fibre diameter (CVFD) is also of some importance, as high CVFD is usually associated with low staple strength. CVFD is controlled by genetics and influenced by fluctuations in nutrition.

Ways to influence diameter

Set breeding objectives for the flock, and design a breeding program to meet those objectives. Choose a ram source with similar objectives that provides objective information on its sires to clarify buying decisions.

'Fining up' the flock through breeding is a long-term process but need not compromise wool cut or other traits.

In higher rainfall areas, sheep can be run at a high stocking rate to maximise wool cut per hectare. Understocked sheep cut more wool per head but less per hectare, and the wool has a higher fibre diameter. Consider lambing in spring rather than autumn to match feed demand with supply.

Apply grazing management techniques to maintain a reasonably constant plane of nutrition, minimising fluctuations in diameter along the fibres.

Tools such as rapid in-shed micron testing with Laserscan or OFDA can help achieve breeding objectives and prepare premium, finer fleece lines during classing.

As a rule of thumb, keep all the wool from similar sheep together. A fine line strategy is only likely to give a net benefit if you have individual measurements for each fleece (visual classing is not precise enough), and where premiums increase steeply for decreasing fibre diameter (that is, the clip should average below 21um as a guide only).