The distinction between short-run and long-run costs

In economics, the time frame affects how firms can adjust their production costs. The short run and long run differ in terms of fixed and variable factors, influencing how costs change with output.

Short-run costs

At least one factor of production is fixed, such as factory size. Firms operate on a specific short-run average cost (SRAC) curve. As output increases, firms add more variable factors (like labour), moving along the SRAC curve.

Long-run costs

All factors of production can be varied, allowing firms to adjust everything, including capital and technology. This enables firms to shift to a new SRAC curve.

Firms aim to minimise costs for any given output. In the short run, limitations from fixed factors may prevent this, but the long run offers flexibility to optimise resource use.

The long-run average cost curve and its relationship to short-run curves

The long-run average cost (LRAC) curve represents the lowest possible average cost for each level of output when all factors can be adjusted. It acts as an 'envelope' that outlines the minimum costs achievable in the long run.

Features of the LRAC curve

• The LRAC curve is formed by connecting the lowest points of multiple SRAC curves, each corresponding to a different scale of fixed factors (e.g., different factory sizes).
• SRAC curves can touch the LRAC curve but cannot dip below it, as the LRAC shows the absolute minimum cost achievable.
• To operate on the LRAC curve at a specific output, a firm must use the optimal combination of all factors of production, which is only possible in the long run when no factors are fixed.
• There is always an SRAC curve that touches the LRAC at both curves' minimum points.

How internal economies and diseconomies of scale shape the LRAC curve

The shape of the LRAC curve is primarily influenced by internal economies and diseconomies of scale, which determine how average costs change as output expands within a firm.

Internal economies of scale

These occur when average costs decrease as output increases, causing the LRAC curve to slope downwards. Larger output allows for efficiencies like bulk purchasing, specialised machinery, or better division of labour, spreading fixed costs over more units.

Internal diseconomies of scale

These arise when average costs increase with higher output, leading the LRAC curve to slope upwards. Issues such as management overload, communication breakdowns, or resource strain can emerge in very large operations, outweighing efficiency gains.

Net effect on the LRAC curve

• The overall shape is U-like: initially downward-sloping due to economies, reaching a minimum (optimal output), then upward-sloping from diseconomies.
• At any output level, a firm might experience both economies and diseconomies simultaneously; the net impact depends on which is stronger, determining if average costs fall or rise.

The impact of external economies and diseconomies on the LRAC curve

External factors, beyond a single firm's control, can shift the entire LRAC curve by affecting costs across an industry or region.

External economies of scale

These lower average costs at all output levels, shifting the LRAC curve downwards.

Examples of downward shifts:

• Industry-wide improvements like better infrastructure, skilled labour pools, or technological advancements.
• New software that enhances efficiency for all firms in a sector.

External diseconomies of scale

These increase average costs at all output levels, shifting the LRAC curve upwards.

Examples of upward shifts:

• Rising raw material prices due to high demand.
• Regulatory changes such as higher environmental taxes on polluting industries like chemical manufacturing.

Other influences causing LRAC shifts

• Taxation changes - An increase in business taxes raises costs uniformly, shifting the LRAC upwards; a decrease shifts it downwards.
• Technological advancements - Innovations like robotic systems can reduce costs by improving factor efficiency, causing a downward shift in the LRAC for all relevant output levels.